bluuebunny/crossref_metadata_2025 huggingface dataset:
Role of nitric oxide in adrenal catecholamine secretion in anesthetized dogs
Authors: Nagayama Takahiro , Hosokawa Akio , Yoshida Makoto , Suzuki-Kusaba Mizue , Hisa Hiroaki , Kimura Tomohiko , Satoh Susumu
Published: December 2017

We examined the role of nitric oxide (NO) in adrenal catecholamine secretion in response to splanchnic nerve stimulation (SNS) and exogenous acetylcholine (ACh) in anesthetized dogs. The NO synthase inhibitor N ω-nitro-l-arginine methyl ester (l-NAME), NO donor 3-(2-hydroxy-1-methyl-2-nitrosohydrazino)- N-methyl-1-propanamine (NOC 7), and ACh were administered intra-arterially into the adrenal gland. The increases in catecholamine output induced by ACh (0.75–3 μg) were enhanced byl-NAME (0.1–1 mg/min) and inhibited by NOC 7 (0.2–2 μg/min). Inhibition by NOC 7 (2 μg/min) was observed during treatment withl-NAME (1 mg/min). The increases in catecholamine output induced by SNS (1–2 Hz) were inhibited byl-NAME and by NOC 7. No inhibitory effect of NOC 7 was observed during treatment withl-NAME. These results suggest that NO may play an inhibitory role in the regulation of adrenal catecholamine secretion in response to exogenous ACh.
Poor relationship between arterial [lactate] and leg net release during exercise at 4,300 m altitude
Authors: Brooks George A. , Wolfel Eugene E. , Butterfield Gail E. , Cymerman Allen , Roberts Amy C. , Mazzeo Robert S. , Reeves John T.
Published: December 2017

We evaluated the hypotheses that on acute exposure to hypobaric hypoxia, sympathetic stimulation leads to augmented muscle lactate production and circulating [lactate] through a β-adrenergic mechanism and that β-adrenergic adaptation to chronic hypoxia is responsible for the blunted exercise lactate response after acclimatization to altitude. Five control and 6 β-blocked men were studied during rest and exercise at sea level (SL), on acute exposure to 4,300 m (A1), and after a 3-wk sojourn at altitude (A2). Exercise was by leg cycling at 49% of SL peak O2 consumption (V˙o 2 peak) (65% of altitude V˙o 2 peak or 87 ± 2.6 W); β-blockade was by propranolol (80 mg 3× daily), femoral arterial and venous blood was sampled; leg blood flow (Q˙) was measured by thermodilution, leg lactate net release [L˙ = (2) (1-leg Q) venous-arterial concentrationL] was calculated, and vastus lateralis needle biopsies were obtained. Muscle [lactate] increased with exercise and acute altitude exposure but regressed to SL values with acclimatization; β-blockade had no effect on muscle [lactate]. Arterial [lactate] rose during exercise at SL (0.9 ± 0.1 to 1.5 ± 0.3 mM); exercise at A1 produced the greatest arterial [lactate] (4.4 ± 0.8 mM), and exercise at A2 an intermediate response (2.1 ± 0.6 mM). β-Blockade reduced circulating [lactate] ∼45% during exercise under all altitude conditions. L˙ increased transiently at exercise onset but then declined over time under all conditions. Blood and muscle “lactate paradoxes” occurred independent of β-adrenergic influences, and the hypotheses relating the blood lactate response at altitude to β-adrenergic mechanisms are rejected. During exercise at altitude, arterial [lactate] is determined by factors in addition to hypoxemia, circulating epinephrine, and net lactate release from active muscle beds.
Differential regulation of uncoupling protein gene homologues in multiple tissues of hibernating ground squirrels
Authors: Boyer Bert B. , Barnes Brian M. , Lowell Bradford B. , Grujic Danica
Published: December 2017

Nonshivering thermogenesis in brown adipose tissue (BAT) provides heat through activation of a mitochondrial uncoupling protein (UCP1), which causes futile electron transport cycles without the production of ATP. Recent discovery of two molecular homologues, UCP2, expressed in multiple tissues, and UCP3, expressed in muscle, has resulted in investigation of their roles in thermoregulatory physiology and energy balance. To determine the expression pattern of Ucp homologues in hibernating mammals, we compared relative mRNA levels of Ucp1, -2, and -3 in BAT, white adipose tissue (WAT), and skeletal muscle of arctic ground squirrels ( Spermophilus parryii) hibernating at different ambient and body temperatures, with levels determined in tissues from ground squirrels not in hibernation. Here we report significant increases in mRNA levels for Ucp2 in WAT (1.6-fold) and Ucp3 in skeletal muscle (3-fold) during hibernation. These results indicate the potential for a role of UCP2 and UCP3 in thermal homeostasis during hibernation and indicate that parallel mechanisms and multiple tissues could be important for nonshivering thermoregulation in mammals.
Renal denervation supersensitivity revisited
Authors: Lohmeier Thomas E. , Reinhart Glenn A. , Mizelle H. Leland , Han Maohao , Dean Mark M.
Published: December 2017

To determine whether the chronically denervated kidney is supersensitive to either physiological or pathophysiological plasma levels of norepinephrine (NE), studies were conducted in conscious dogs subjected to unilateral renal denervation and surgical division of the urinary bladder into hemibladders to allow separate 24-h urine collection from denervated and innervated kidneys. Plasma NE concentration was increased by chronic infusion of NE (4–5 days) at rates of 25, 100, and 200 ng ⋅ kg−1 ⋅ min−1. Twenty-four-hour control values for mean arterial pressure (MAP), plasma NE concentration, and ratios for urinary sodium and potassium excretion from denervated and innervated kidneys (Den/Inn) were 94 ± 4 mmHg, 145 ± 24 pg/ml, 1.05 ± 0.05, and 0.97 ± 0.07, respectively. With infusions of NE producing plasma levels of NE of up to ∼3,000 pg/ml or plasma concentrations of NE at least threefold greater than present under most pathophysiological conditions and during acute activation of the sympathetic nervous system, there were no significant long-term changes in MAP or relative excretion rates of sodium and potassium from denervated and innervated kidneys. In marked contrast, pharmacological plasma levels of NE (∼7,000 pg/ml) produced chronic increases in MAP (to 116 ± 2% of control) and sustained reductions in Den/Inn for urinary sodium and potassium excretion to 57 ± 4 and 68 ± 5% of control, respectively, indicating a lower excretion rate of these electrolytes from denervated vs. innervated kidneys. We conclude that the chronically denervated kidney does not exhibit an exaggerated antinatriuretic response to either physiological or pathophysiological levels of circulating NE. It is therefore unlikely that renal denervation supersensitivity is a confounding issue in studies employing chronic renal denervation to elucidate the role of the renal nerves in the regulation of sodium excretion.
Altered regulation of bladder nerve growth factor and neurally mediated hyperactive voiding
Authors: Clemow David B. , Steers William D. , McCarty Richard , Tuttle Jeremy B.
Published: December 2017

Elevated bladder smooth muscle cell (BSMC) nerve growth factor (NGF) secretion and related neuroplasticity are associated with hyperactive voiding in spontaneously hypertensive rats (SHRs: hypertensive, behaviorally hyperactive), compared with control Wistar-Kyotos (WKYs). We used two inbred strains (WKHT: hypertensive; WKHA: hyperactive) to further investigate this phenomenon. WKHA BSMCs secreted higher basal levels of NGF than WKHT BSMCs. Antagonists did inhibit NGF output in WKHA but not WKHT cultures. Thus augmented basal secretion of NGF cosegregates with a hyperactive phenotype, whereas a lack of regulatory inhibition of NGF output cosegregates with a hypertensive phenotype. Bladder norepinephrine content paralleled NGF content, with WKHTs > SHRs > WKHAs > WKYs, providing evidence that a lack of inhibition is the greatest contributor to elevated bladder NGF and noradrenergic innervation. Protein kinase C (PKC) agonists affected NGF production differentially depending on strain, suggesting that altered PKC signaling may contribute to strain differences in NGF secretion. Finally, 6-h voiding frequency differed between the strains, with SHRs > WKHTs = WKHAs > WKYs. Thus aspects of both the hypertensive and hyperactive phenotypes may be associated with elevated SHR bladder NGF and hyperactive voiding.
Cytokine-induced fever in obese (fa/fa) and lean (Fa/Fa) Zucker rats
Authors: Plata-Salamán Carlos R. , Peloso Elizabeth , Satinoff Evelyn
Published: December 2017

In earlier work, we reported that genetically obese ( fa/ fa) Zucker rats exhibited significantly greater anorexia than did lean ( Fa/ Fa) Zucker rats to intracerebroventricular infusion of interleukin (IL)-1β. Here, we investigated the fever response of obese ( fa/ fa) and lean ( Fa/ Fa) Zucker rats to intracerebroventricular microinfusion of IL-1β as well as to the following other cytokines: IL-2, IL-6, and tumor necrosis factor-α (TNF-α). Core body temperature was monitored by a radiotelemetry system in freely moving rats. The results show that 1) both IL-1β and IL-6 induce fevers in obese and lean rats; 2) IL-1β induces a significantly higher fever response in obese rats than it does in lean rats; 3) IL-6 induces a significantly higher fever response in lean rats than it does in obese rats; 4) IL-2 induces a moderate fever response in lean but not obese rats; 5) TNF-α induces a similar fever response in obese and lean rats; and 6) the fevers induced by each effective cytokine have different time courses. Thus obese ( fa/ fa) and lean ( Fa/ Fa) Zucker rats show differential responsiveness to the intracerebroventricular microinfusion of various classes of cytokines. This suggests that genetic obesity in the fa/fa Zucker rat is associated with differential cytokine action on thermoregulatory mechanisms.
Evidence for induction of a phosphate appetite in juvenile rats
Authors: Sweeny Joseph M. , Seibert H. Edward , Woda Craig , Schulkin Jay , Haramati Aviad , Mulroney Susan E.
Published: December 2017

This study examined whether dietary phosphate (Pi) restriction stimulates an appetite for Pi in the juvenile rat, which normally has a high metabolic Pi demand for growth. Juvenile Wistar rats were placed in individual cages with unrestricted access to tap water and a low (LPD, 0.02% Pi) or normal Pi diet (NPD, 0.6% Pi) for 7 days. On day 8, both groups of rats were given unlimited access to a solution of 0.3 M potassium phosphate water (PiH2O) for 8 additional days. Rats fed LPD consumed 70–100% more PiH2O then those rats fed NPD ( P < 0.001). The increase in PiH2O intake resulted in a marked rise in the growth rate of rats fed LPD during days 8–15. A similar Pi intake was inducible after only 2 days of LPD and was associated with significant reductions in both plasma and cerebrospinal fluid (CSF) Pi levels; these levels remained low throughout Pi restriction, despite a significant PiH2O intake. Furthermore, the renal adaptation to enhance Pi reabsorption (TmPi) during Pi deprivation remained elevated despite enhanced PiH2O intake. Replenishment with a high-Pi diet rapidly quenched the PiH2O appetite and was associated with restoration of both plasma and CSF Pi levels. These findings suggest that an appetite for Pi can be induced in juvenile rats, perhaps through lowered plasma and CSF Pi levels. This behavioral response may serve as an additional mechanism to maintain an adequate supply of Pi necessary for growth and development of the animal.
Nutrients regulate diamine oxidase release from intestinal mucosa
Authors: Wollin Armin , Wang Xiaolin , Tso Patrick
Published: December 2017

Diamine oxidase is continuously released from the intestinal mucosa and carried to the circulation by the lymphatics. The effect of nutrients on this release was examined. Rats were prepared with duodenal and intestinal lymph cannulas. Test mixtures of lipid emulsions containing triolein, oleic acid, or tricaprylin and solutions of carbohydrate and protein were infused into the duodenum. The enzyme release and triglyceride transport were determined and in some experiments were done in the presence and absence of Pluronic L-81, an inhibitor of chylomicron formation, and aminoguanidine, an inhibitor of diamine oxidase activity. The data indicate that nonlipid nutrients did not increase diamine oxidase activity in the intestinal lymph, but the mucosal tissue content was significantly reduced in the distal small intestine, particularly after protein infusion. Triglycerides and fatty acids increased diamine oxidase in the intestinal lymph, and the longer-chain triglyceride was more effective. Inhibition of triglyceride transport did not interfere with the enzyme release, and the inhibition of diamine oxidase activity had no significant effect on lipid absorption. According to our observations, only lipids increase intestinal lymph diamine oxidase. Nonfat nutrients appear to increase diamine oxidase in the intestinal lumen. Diamine oxidase is not directly required for lipid absorption.
Differential arterial baroreflex regulation of renal, lumbar, and adrenal sympathetic nerve activity in the rat
Authors: Scislo Tadeusz J. , Augustyniak Robert A. , O’Leary Donal S.
Published: December 2017

Lumbar (LSNA), renal (RSNA), or adrenal sympathetic nerve activity (ASNA) is most commonly used as an index of sympathetic nerve activity in investigations of arterial baroreflex control in the rat. Although differential regulation of sympathetic outputs to different organs has been extensively studied, no direct and simultaneous comparisons of the full range of baroreflex reactivity have been described for these sympathetic outputs. Therefore, we compared steady-state sigmoidal baroreflex stimulus-response curves (via phenylephrine-nitroprusside infusion) for RSNA recorded simultaneously with LSNA or ASNA in urethan-chloralose-anesthetized male Sprague-Dawley rats. Characteristics of the baroreflex curves differed significantly between all three sympathetic outputs. ASNA exhibited the greatest range of baroreflex regulation, the highest upper level of activity, and the widest distribution of the gain over a broad range of mean arterial pressure (MAP). RSNA exhibited greater gain than LSNA. LSNA showed the smallest range and maximal inhibition in comparison to other sympathetic outputs. However, all three nerves responded similarly to baroreflex stimulation and unloading in the range in MAP close to the operating point. We conclude that baroreflex regulation of sympathetic activity shows wide regional variability in gain, range, and maximal inhibition. Therefore, the entire stimulus-response relationship should be considered in comparing regional sympathetic responses.
Cytokine modulation by PX differently affects specific acute phase proteins during sepsis in rats
Authors: Voisin Laure , Breuillé Denis , Ruot Benoît , Rallière Cécile , Rambourdin Fabienne , Dalle Michel , Obled Christiane
Published: December 2017

To explore the regulation of the acute phase response in vivo, the effects of pentoxifylline (PX) treatment (100 mg/kg ip 1 h before infection) were investigated in infected and pair-fed rats 2 and 6 days after an intravenous injection of live bacteria ( Escherichia coli). PX treatment prevented the increase in plasma tumor necrosis factor (TNF)-α (peak 1.5 h after the infection) and resulted in an 84 and 61% inhibition of plasma interleukin (IL)-1β and IL-6, respectively (peaks at 3 h). Plasma corticosterone kinetics were not modified by the treatment. Infection increased α1-acid glycoprotein (AGP), α2-macroglobulin (A2M), and fibrinogen plasma concentrations and decreased albumin levels. PX significantly reduced AGP plasma concentration as early as day 2 in infected animals but reduced A2M and fibrinogen plasma levels only at day 6. The treatment had no effect on the albumin plasma concentration. Hepatic AGP and fibrinogen mRNA levels increased in infected rats, whereas those of A2M were unchanged and those of albumin were decreased. Two days after infection, AGP and fibrinogen mRNA levels were reduced in treated infected animals. PX was ineffective in modifying those of A2M and albumin. These data demonstrate, in vivo, that different acute phase proteins are individually regulated in sepsis. The in vivo effects of PX treatment support the hypothesis that TNF-α plays an important role in the regulation of AGP production, whereas other factors seem to be involved in the regulation of A2M, fibrinogen, and albumin expression.
Effects of long-term vasopressin receptor stimulation on medullary blood flow and arterial pressure
Authors: Cowley Allen W. , Skelton Meredith M. , Kurth Theresa M.
Published: December 2017

Studies were carried out using instrumented unanesthetized rats to determine the long-term effects of arginine vasopressin (AVP) and a specific vasopressin V1 receptor agonist (V1AG; [Phe2, Ile3, Orn8]- vasopressin) on the renal medullary blood flow and arterial blood pressure. It was hypothesized that the hypertension observed with chronic medullary infusion of a V1 receptor agonist may be associated with a sustained reduction of blood flow, whereas infusion of AVP may fail to produce a sustained reduction of blood flow and thereby be unable to produce hypertension. Uninephrectomized Sprague-Dawley rats were prepared with implanted renal cortical and medullary optical fibers for daily measurements of cortical and medullary blood flow using laser-Doppler flowmetry techniques. An implanted renal medullary interstitial infusion catheter delivered either AVP or a specific V1AG at a dose of 2 ng ⋅ kg−1 ⋅ min−1over a period of 5 days. The V1AG produced no change of cortical blood flow but a chronic 35% reduction of medullary blood flow ( P < 0.05) and mild hypertension (11 ± 4 mmHg, P < 0.05). AVP produced only an initial, nonsignificant 1- to 2-day reduction of medullary blood flow (−13%) and failed to raise arterial pressure significantly. We conclude that a sustained V1AG response is necessary to achieve a chronic reduction of medullary blood flow and hypertension. The present data are consistent with the idea that chronic stimulation of V2receptors by AVP offsets the vasoconstrictor and hypertension actions of AVP-induced stimulation of medullary V1 receptors.
Effect of a chronic stress on CRF neuronal activity and expression of its type 1 receptor in the rat brain
Authors: Bonaz Bruno , Rivest Serge
Published: December 2017

The purpose of this study was to compare the effect of an acute versus a chronic immobilization stress on the genetic expression of c- fos and corticotropin-releasing factor type 1 receptor (CRF1receptor) in the paraventricular nucleus (PVN) of the rat hypothalamus. Male Sprague-Dawley rats were exposed to either a single 90-min immobilization stress or the same session for 11 consecutive days. Animals were deeply anesthetized before (control); immediately, 1.5, 3, 6, or 12 h after the acute stress; or after the last session of the repeated exposures to immobilization. Coronal frozen sections (30 μm) of the brains were cut and mRNAs encoding the rat c- fos and CRF1 receptor were assayed by in situ hybridization histochemistry using35S-labeled riboprobes. Localization of these transcripts within PVN CRF-immunoreactive (ir) neurons was also determined. The expression of the mRNA encoding either c- fos or CRF1 receptor was barely detectable to low in the PVN of control animals, but the acute stress session induced a robust signal for both transcripts in this endocrine nucleus. Numerous CRF-ir neurons were positive for the gene encoding either c- fos or CRF1 receptor in the PVN of acutely stressed animals. In contrast, the PVN of chronically stressed animals displayed a significantly lower CRF1 receptor mRNA signal after the last stress session. In these animals, stress-induced transcription of c- fos mRNA occurred in the magnocellular PVN 90 min after the end of the last stress session but only a low signal was detected in the parvocellular division. Moreover, very few CRF-ir neurons of the PVN expressed either the CRF1 receptor or c- fos transcript in chronically stressed rats. These data provide evidence for an adaptive cellular mechanism involving an attenuated action of CRF within the PVN in response to repeated homotypic stress exposures.
Meal patterns associated with the age-related decline in food intake in the Fischer 344 rat
Authors: Blanton Cynthia A. , Horwitz Barbara A. , Murtagh-Mark Carol , Gietzen Dorothy W. , Griffey Stephen M. , McDonald Roger B.
Published: December 2017

We previously reported that aging Fischer 344 (F344) rats display a spontaneous, rapid loss in body weight associated with decreased food intake near the end of life. Here, we describe the specific changes in feeding patterns underlying this reduced intake. Nine male F344 rats, aged 25 mo, were monitored continuously until 7 days after the onset of spontaneous rapid weight loss (i.e., senescence). Regardless of age at death (25.5–32.5 mo), all senescent rats demonstrated a similar pattern of decreased food intake. They ate significantly smaller meals (g/meal) of shorter duration during spontaneous rapid weight loss compared with their period of weight stability (presenescence). However, no differences occurred in the number of meals eaten per day. Rapid weight loss had no effect on the rats’ selection of preferred diets. Serum levels of the hormone leptin were not higher in the senescent vs. age-matched presenescent rats, nor was the incidence of common disease different in senescent animals. Moreover, the area of the pituitary-hypothalamus interface, measured to identify possible hypothalamic compression, was similar in the senescent rats and an age-matched, presenescent control group despite significantly greater pituitary size in the former. Our data show that simultaneous with rapid spontaneous weight loss, aging rats demonstrate significant changes in feeding patterns suggestive of earlier satiation. These feeding alterations do not result from loss of ability to select for palatable food, elevated serum leptin levels, specific pathology, or hypothalamic compression.
High-fat diet preference and overeating mediated by postingestive factors in rats
Authors: Lucas François , Ackroff Karen , Sclafani Anthony
Published: December 2017

The role of postingestive factors in the preference for and overconsumption of high-fat (HF) foods, relative to high-carbohydrate (HC) foods, was investigated using a self-regulated intragastric feeding procedure. On one-bottle training days, rats drank one flavored saccharin solution [conditioned stimulus (CS) + HF] paired with intragastric infusions of an HF liquid diet, a second flavored solution (CS+HC) paired with an HC liquid diet, and a third flavored solution (CS−) paired with intragastric water. The diets had the same energy and protein content; the CS solutions and infusions along with chow were available ad libitum. The rats drank more CS and self-infused more diet on HF than HC training days. In two-bottle choice tests, the rats preferred the CS+HF to the CS+HC and both CS+HF and CS+HC to the CS−. The rats consumed more CS+HF than CS+HC by taking more bouts per day; bout sizes did not reliably differ. In a subsequent experiment, rats preferred the CS+HF even though diet intakes in training were matched. In a final experiment, the CS+HC and CS+HF intakes were equated in training by diluting the HC diet. Now the rats did not reliably prefer the CS+HF to the CS+HC, yet caloric intakes were much higher on CS+HF than CS+HC training days. Thus, relative to an isocaloric HC diet, the postingestive effects of HF diets stimulate overeating and condition a stronger flavor preference. Reduced satiety rather than increased reinforcement may be the direct promoter of overeating. However, postingestive reinforcement may enhance the selection of HF foods when a choice of HF and HC foods is available.
M2muscarinic receptor contributes to contraction of the denervated rat urinary bladder
Authors: Braverman Alan S. , Luthin Gary R. , Ruggieri Michael R.
Published: December 2017

In vitro bladder contractions in response to cumulative carbachol doses were measured in the presence of selective muscarinic antagonists from rats that had their major pelvic ganglion bilaterally removed. Denervation induced both hypertrophy and a supersensitivity of the bladders to agonist. The affinities in control bladders for antagonism of carbachol-induced contractions were consistent with M3-mediated contractions. Affinities in denervated bladders for 4-diphenlacetoxy- N-methylpiperidine methiodide (8.5) and p-fluoro hexahydrosilodifenidol (6.6) were consistent with M2-mediated contractions, although the methoctramine affinity (6.5) was consistent with M3-mediated contractions. Subtype-selective immunoprecipitation of muscarinic receptors revealed a 50% increase in total and a 60% increase in M2receptor density with no change in M3receptor density in denervated bladders compared with normal or sham-operated controls. This increase in M2receptor density is consistent with the change in affinity of the antagonists for inhibition of carbachol-induced contractions and may indicate that M2receptors or a combination of M2and M3receptors directly mediates smooth muscle contraction in the denervated bladder.
Fetal tissue containing the suprachiasmatic nucleus restores multiple circadian rhythms in old rats
Authors: Li Hua , Satinoff Evelyn
Published: December 2017

The suprachiasmatic nucleus (SCN) is the major circadian pacemaker in mammals. When fetal tissue containing the SCN is transplanted into young rats whose circadian rhythms have been abolished by SCN lesions, the rhythms gradually reappear. Circadian rhythms in many rats deteriorate or disappear with age. The rationale of the present study was that old rats with poor circadian rhythms resemble young rats with SCN lesions. If there is a similar mechanism underlying this resemblance, then fetal tissue containing the SCN should restore rhythms in old rats. Therefore, we implanted such tissue into the third ventricle of intact aged rats with poor circadian rhythms. Body temperature, locomotor activity, and/or drinking were measured simultaneously within subjects. Grafts and hosts were stained immunocytochemically for vasoactive intestinal polypeptide (VIP), arginine vasopressin (AVP), and neuropeptide Y (NPY). Of 23 SCN grafts, 14 were viable (cells observable with Nissl or peptide staining). In 7 of the 14 aged hosts, up to three circadian rhythms were improved or restored. VIP cells were always observable, which was not the case for AVP cells or NPY fibers. In the other seven hosts, no circadian rhythm was improved. Compared with the successful grafts, these unsuccessful grafts had similar amounts of AVP and NPY staining but significantly less VIP cell and/or fiber staining. Fetal cerebellar grafts, which do not contain any of the three peptides, did not improve or restore any rhythms. Thus the degeneration of circadian rhythms in aged rats may be due, at least in part, to deterioration of the aged SCN and in particular, to a loss of function of VIP-containing neurons.
Amiloride-sensitive Na+channels in pelvic uroepithelium involved in renal sensory receptor activation
Authors: Kopp Ulla C. , Matsushita Kazumichi , Sigmund Rita D. , Smith Lori A. , Watanabe Shigeru , Stokes John B.
Published: December 2017

Stretching the renal pelvic wall increases ipsilateral afferent renal nerve activity (ARNA). This response is enhanced by inhibiting Na+-K+-ATPase with ouabain, suggesting a modulatory role for intracellular Na+in the activation of mechanosensitive neurons. The messenger RNA for α-, β-, and γ-subunits of epithelial Na+channels (ENaC) is found in collecting duct cells. Because ENaC subunits show homology with genes involved in mechanosensation, we examined whether ENaC mRNA could be found in the pelvic wall and whether the ARNA response to increased renal pelvic pressure was modulated by blockers of the Na+channel. α-, β-, and γ-subunits are present in the pelvis. The messenger RNA for the β- and γ-subunits is readily detected by in situ hybridization throughout the uroepithelium. The ARNA response to increased renal pelvic pressure was reduced by 53 ± 10% and 40 ± 10% ( P < 0.01) by renal pelvic perfusion with the inhibitors amiloride and benzamil, respectively. Amiloride inhibited the ouabain-induced enhancement of the ARNA response to increased renal pelvic pressure. The magnitude of this inhibition was inversely correlated with the magnitude of the amiloride-mediated blockade of the ARNA response to increased renal pelvic pressure ( P < 0.001). Amiloride also reduced the ARNA response to renal pelvic administration of substance P, a mediator of the ARNA response to increased renal pelvic pressure. We conclude that the ENaC complex in the pelvic uroepithelium participates in the activation of renal pelvic mechanosensitive neurons.
Characterization of responses to neurokinin A in the isolated perfused guinea pig heart
Authors: Hoover Donald B. , Chang Yingzi , Hancock John C.
Published: December 2017

Goals of this study were to identify and characterize effects of neurokinin A (NKA) in isolated guinea pig hearts. Bradycardia, augmentation of ventricular contractions, and reduction of perfusion pressure were prominent responses to bolus injections of NKA (0.25–25 nmol). NKA was more potent than substance P (SP) in causing bradycardia but did not differ in potency for lowering perfusion pressure. Doses of SP of 25 nmol or less decreased ventricular force, whereas 100 nmol caused a biphasic response. The percent decrease in heart rate produced by 25 nmol NKA was reduced from 58.0 ± 4.8 to 39.6 ± 3.5% in the presence of 1 μM atropine ( n = 5). The positive inotropic response to 25 nmol of NKA in spontaneously beating hearts was replaced by a negative inotropic response during pacing (22.5 ± 3.3% increase vs. 11.7 ± 1.7% decrease, n = 5). Reserpine pretreatment did not affect the positive inotropic response to NKA. Specific binding sites for125I-labeled NKA were localized to intracardiac ganglia and coronary arteries but not to myocardium. It was concluded that 1) negative chronotropic responses to NKA involve cholinergic and noncholinergic mechanisms, and 2) the positive inotropic response is an indirect action.
Glutamate in the nucleus of the solitary tract activates both ionotropic and metabotropic glutamate receptors
Authors: Foley C. Michael , Moffitt Julia A. , Hay Meredith , Hasser Eileen M.
Published: December 2017

Glutamate is the proposed neurotransmitter of baroreceptor afferents at the level of the nucleus of the solitary tract (NTS). Blockade of ionotropic glutamate receptors with kynurenic acid blocks the arterial baroreflex but, paradoxically, does not abolish the response to exogenous glutamate. This study tested the hypothesis that exogenous glutamate in the NTS activates both ionotropic and metabotropic glutamate receptors (mGluRs). In urethan-anesthetized rats, unilateral microinjections of glutamate into the NTS decreased mean arterial pressure, heart rate, and lumbar sympathetic nerve activity. The cardiovascular response to injection of glutamate was not altered by NTS blockade of mGluRs with α-methyl-4-carboxyphenylglycine (MCPG). Blockade of ionotropic glutamate receptors with kynurenic acid attenuated the response to glutamate injection. After combined NTS injection of MCPG and kynurenic acid, the response to glutamate was blocked. These data suggest that exogenous glutamate microinjected into the NTS acts at both ionotropic glutamate receptors and mGluRs. In addition, blockade of both classes of glutamate receptors is required to block the cardiovascular response to microinjection of glutamate in the NTS.
Joint recovery of pulsatile and basal hormone secretion by stochastic nonlinear random-effects analysis
Authors: Keenan Daniel M. , Veldhuis Johannes D. , Yang Ronghua
Published: December 2017

We present a nonlinear random-effects stochastic differential equation (SDE) model of combined basal and pulsatile hormone secretion with a series-specific hormone half-life and conditional pulse times. The construct uses a three-parameter pulse shape (generalized gamma function) to allow variably skewed secretory bursts superimposed on a finite basal hormone secretion rate. The analysis imbeds stochastic elements at three levels: a variable mass of hormone accumulation (of which the random effect is a part) during interpulse intervals, nonuniform secretion with hormone admixture into the circulation, and technical (sampling and assay) experimental uncertainty. We implement maximum likelihood estimates of secretory parameters (basal and pulsatile secretion and half-life) with asymptotic standard errors. The model applied to illustrative human luteinizing hormone (LH) time series suggests contrasts in basal LH secretion rates (e.g., greater in postmenopausal women than men) and LH secretory burst mass (e.g., higher in older women), but not LH burst frequency or distributional LH half-lives (7–40 min). For validation, in two infused (human recombinant) LH profiles, we implement partially constrained mono- and biexponential versions of the model with fixed (a priori assumed) versus variable LH basal secretion rates. We conclude that a statistically supported, nonlinear, random effects, SDE-based construct can evaluate jointly basal and pulsatile LH secretory rates and LH half-life in 24 h, episodically varying serum LH concentration profiles. This new reduced-parameter analytic strategy should be useful to explore further the pathophysiological mechanisms of altered neurohormone secretion.
Effect of ovariectomy in heart failure-prone SHHF/Mcc-facp rats
Authors: Sharkey Leslie C. , Holycross Bethany J. , Park Sonhee , McCune Sylvia A. , Hoversland Roger , Radin M. Judith
Published: December 2017

The importance of the loss of ovarian function to the progression of hypertension and heart disease in women is controversial. We investigated whether ovariectomy would accelerate development of hypertension, congestive heart failure, and neurohumoral activation in adult spontaneous hypertension heart failure (SHHF) rats, a genetic model of heart failure. Six months after ovariectomy, no significant differences between control and ovariectomized rats were seen in systolic or diastolic blood pressure, left ventricular fractional shortening by echocardiography, or heart weight. Percent V1 myosin isozyme was significantly lower in ovariectomized rats. Northern blot analysis failed to show significant differences between groups in expression of hepatic angiotensinogen, renal renin, or left ventricular atrial or brain natriuretic peptide mRNA. In a second experiment, serial measures of systolic pressure and left ventricular shortening fractions failed to document a significant difference between control and ovariectomized rats as they developed heart failure, although there was a significant decline in shortening fraction in both groups at the age when regular estrous cycling naturally ceases. Survival time was similar between groups. In summary, ovariectomy of adult SHHF rats does not appear to affect the progression of genetically programmed hypertension and heart failure in this model.
Thermogenesis is β3- but not β1-adrenergically mediated in rat brown fat cells, even after cold acclimation
Authors: Zhao Jin , Cannon Barbara , Nedergaard Jan
Published: December 2017

To examine if acclimation of rats to cold led to alterations in the coupling between different β-receptor subtypes and thermogenesis in brown fat cells, we investigated the adrenergic response patterns in brown fat cells isolated from warm-acclimated (28°C) and cold-acclimated (4°C) rats. In the cells from warm-acclimated rats, the relative affinities (EC50) for different agonists (isoprenaline, BRL-37344, norepinephrine, CGP-12177, dobutamine, and salbutamol) were those expected from their interaction with a β3-receptor. The response to norepinephrine was competitively inhibited by propranolol with a p A2of ≈6, implying interaction at the β3-receptor. No evidence for a β1-receptor-mediated response to the β1-selective agonist dobutamine could be obtained; the low-affinity response observed was most likely through the β3-receptor. The β1-antagonist ICI-89406 could not inhibit a specific fraction of the thermogenic response to norepinephrine. Thus β3-receptors were the only β-receptors involved in the control of thermogenesis in brown fat cells from warm-acclimated rats. A modified method of preparation was developed to isolate functional cells from cold-acclimated animals. Also in these cells, the β-receptor coupled to thermogenesis was the β3-receptor, although the response was desensitized with an approximately sevenfold shift in EC50values. The p A2for propranolol inhibition of norepinephrine-induced thermogenesis was also 6 here, and that for ICI-89406 was 5.5, also implying interaction at the β3-receptor. Thus acclimation to cold did not alter the β-adrenergic receptor subtype (β3) involved in the control of thermogenesis.
IL-6 is essential in TNF-α-induced fever
Authors: Sundgren-Andersson Anna K. , Östlund Pernilla , Bartfai Tamas
Published: December 2017

Tumor necrosis factor-α (TNF-α) is a pleiotropic cytokine that orchestrates an array of local and systemic effects. For instance, acute exposure to a high dose of TNF-α results in septic shock and fever. We have used interleukin-1β (IL-1β)- and interleukin-6 (IL-6)-deficient mice, along with their wild-type equivalents, to define a role for TNF-α in fever. Briefly, the mice produced prostaglandin E2-dependent fevers in response to recombinant murine TNF-α (rmTNF-α). Furthermore, rmTNF-α (12 μg/mouse ip) triggered a febrile response in IL-1β-deficient mice as well as in their corresponding wild-type controls. In contrast, the IL-6-deficient mice were resistant to rmTNF-α (4.5 μg/mouse ip), although their wild-type counterparts readily mounted a fever. In the IL-6-deficient mice, moreover, the febrile response to rmTNF-α could be restored by a central administration of rat recombinant IL-6 (500 ng/mouse icv). We thus conclude that TNF-α can trigger fever independent of IL-1β but dependent on IL-6. We also suggest that central, rather than peripheral, IL-6 (plasma IL-6 was measured 2 h after pyrogenic challenge) is essential in TNF-α-induced fever.
Renal effects of leptin in normotensive, hypertensive, and obese rats
Authors: Villarreal Daniel , Reams Garry , Freeman Ronald H. , Taraben Amir
Published: December 2017

The hemodynamic, hormonal, and renal excretory effects of intravenous bolus administration of synthetic murine leptin were examined in groups of anesthetized normotensive (Sprague-Dawley), hypertensive (spontaneously hypertensive), and both lean and obese Zucker rats. In the normotensive animals ( n = 8) an intravenous bolus of 400 μg/kg of leptin produced a significant six- to sevenfold elevation in sodium excretion compared with controls ( n = 8). The onset of natriuresis was delayed for ∼30–45 min. Mean arterial pressure (MAP), creatinine clearance, plasma renin activity (PRA), and plasma aldosterone concentration (PAC) remained unchanged. In contrast, the hypertensive rats were refractory to the natriuretic effects of leptin when infused either with 400 ( n = 8) or 1,600 ( n = 8) μg/kg. Also in these animals MAP, creatinine clearance, PRA, and PAC were unmodified. Finally, whereas lean Zucker rats ( n = 8) responded very similarly to the Sprague-Dawley animals, the natriuretic effect of the hormone was attenuated in the obese Zucker groups. At 400 μg/kg ( n = 8) no natriuresis was elicited, but at 1,600 μg/kg ( n = 8) a modest but significant two- to threefold increment in sodium excretion was observed in the obese rats. In both Zucker groups, MAP, creatinine clearance, PRA, and PAC were unchanged. Collectively, these results demonstrate a significant natriuretic effect of exogenous leptin in the normal rat and a blunted saluretic response in hypertension and obesity. It is suggested that leptin may be a potential salt-excretory factor in normal rats and may function pathophysiologically in obesity and hypertension.
L-type Ca2+current and excitation-contraction coupling in single atrial myocytes from rainbow trout
Authors: Hove-Madsen Leif , Tort Lluis
Published: December 2017

We have examined the contribution of L-type Ca2+current ( ICa) to the activation of contraction in trout atrial myocytes under basal and phosphorylating conditions. The average myocyte length was 197 ± 14 μm, width was 5.5 ± 0.2 μm, and cell capacitance was 36.2 ± 2.2 pF. With 25 μM EGTA in the patch pipette and a stimulation frequency of 0.125 Hz, ICawas 2.6 ± 0.4 pA/pF and it carried a total charge of 0.10 ± 0.01 pC/pF, giving rise to a contraction of 15.2 ± 2.8% of the resting cell length. With a cell volume of 2.4 ± 0.3 pl, the charge carried by ICacorresponded to 14.7 ± 2.2 μmol Ca2+/l nonmitochondrial cell volume (μM). This can account for only 30–40% of the Ca2+binding to the myofilaments during a contraction. Increasing the stimulation frequency from 0.25 to 2 Hz decreased ICaamplitude and charge by 66 ± 5 and 80 ± 3%, respectively. Elevating the pipette EGTA concentration from 25 μM to 5 mM increased ICaamplitude and charge by ∼290%. Both isoproterenol and cAMP increased ICaby ∼230%. The total charge carried by the isoproterenol- or cAMP-stimulated current was increased by 170%. We conclude that the use of high-EGTA concentration may overestimate the total Ca2+carried by ICaunder physiological conditions. Furthermore, the results suggest that, in contrast to previous reports from other lower vertebrates, Ca2+flux through L-type Ca2+channels alone is not sufficient to fully activate contraction in trout atrial myocytes at room temperature.
Quantification of Ca2+uptake in the sarcoplasmic reticulum of trout ventricular myocytes
Authors: Hove-Madsen Leif , Llach Anna , Tort Lluis
Published: December 2017

We measured Ca2+uptake by the sarcoplasmic reticulum (SR) in trout ventricular myocytes, measuring indo 1 fluorescence in permeabilized cells or ionic currents in single myocytes subjected to voltage clamp. Titration of the SR Ca2+pumps with thapsigargin gave a pump site density of 454 pmol/mg cell protein. Lowering the temperature from 20°C to 10 or 5°C reduced the SR Ca2+uptake rate in permeabilized myocytes by 50 and 63%, respectively. Surprisingly, Ca2+leak from the SR also decreased with decreasing temperatures. Exposure of single myocytes to 10 mM caffeine (Caf) induced a cell contracture and an inward ionic current. Neither contracture nor current decreased significantly after rest periods of 120 and 320 s. The inward current was due to Ca2+extrusion by the Na+/Ca2+exchanger (NCX), and the time integral of the exchange current ( INCX) was used to calculate the SR Ca2+content. This gave a steady-state SR Ca2+content of 22.5 ± 2.8 amol Ca2+/pF or 750 μM. When the SR was loaded by depolarizing the cell to +50 mV, the Ca2+content increased with increasing length of the depolarization, reaching a maximum of 52.0 ± 5.9 amol Ca2+/pF. When the cell was depolarized to different voltages for 3 s, a subsequent Caf-induced INCXincreased with increasing voltage. At +100 mV, the Ca2+content was 36.6 ± 3.8 amol/pF, giving a maximal SR Ca2+uptake rate of 12.2 ± 1.2 amol Ca2+⋅ pF−1⋅ s−1or 417 μM/s. We conclude that maximal SR Ca2+content and Ca2+uptake rates can be estimated using specific SR Ca2+loading protocols. Contrary to the general assumption that contraction in lower vertebrates depends largely on transsarcolemmal Ca2+fluxes, we found that although the L-type Ca2+current is insufficient to fully activate contraction, the SR is capable of participating in the regulation of the cytosolic Ca2+during the excitation-contraction coupling in trout ventricular myocytes.
Role of cholinergic receptors and cholinesterase activity in hemodynamic responses to cocaine in conscious rats
Authors: Knuepfer Mark M. , Gan Qi
Published: December 2017

It has been suggested that toxicity to cocaine is related to the relative rate of cocaine metabolism by cholinesterases and to activation of cholinergic receptors either directly or by reflex mechanisms. We examined these possibilities by altering cholinesterase activity and blocking cholinergic receptors in rats prone or resistant to cocaine-induced cardiovascular toxicity. Rats were instrumented with a pulsed Doppler flow probe on the ascending aorta for measurement of cardiac output and cannulated for arterial pressure and heart rate determination. In conscious rats, cocaine (5 mg/kg iv) elicited pressor responses and a delayed bradycardia but cardiac output and systemic vascular resistance responses varied greatly between rats. Pretreatment with the nonspecific cholinesterase inhibitors physostigmine (0.1–0.2 mg/kg) or neostigmine (0.1 mg/kg) reduced the pressor response by diminishing the increase in systemic vascular resistance. In contrast, inhibition of cocaine metabolism with the selective plasma cholinesterase inhibitor tetraisopropyl pyrophosphoramide (0.5 mg/kg) or increasing cholinesterase activity with human butyryl cholinesterase (9.9 mg/kg iv) did not alter hemodynamic responses to cocaine. Administration of atropine methyl bromide (0.5–1 mg/kg iv) alone or with physostigmine to prevent the cholinomimetic effects of physostigmine reduced the cocaine-induced decrease in cardiac output noted in some animals. These data suggest that the cocaine-induced decrease in cardiac output observed in some rats is, at least in part, dependent on activation of muscarinic receptors. In addition, the rate of cocaine metabolism is not critical for the initial hemodynamic responses to cocaine in conscious rats.
Oxidized amino acids in the urine of aging rats: potential markers for assessing oxidative stress in vivo
Authors: Leeuwenburgh Christiaan , Hansen Polly A. , Holloszy John O. , Heinecke Jay W.
Published: December 2017

Oxidative damage of proteins has been implicated in disease and aging. In vitro studies demonstrate that two unnatural amino acids, o,o′-dityrosine and o-tyrosine, are stable markers of protein oxidation. We have investigated the possibility that assaying these compounds in urine could provide a noninvasive way to determine levels of protein oxidation in vivo. Isotope dilution gas chromatography-mass spectrometry was used to quantify levels of o,o′-dityrosine and o-tyrosine in skeletal muscle and urine of aging rats subjected to two interventions: 1) dietary antioxidant supplementation and 2) exercise training. In both sedentary rats and exercise-trained rats, antioxidant therapy reduced levels of protein-bound o,o′-dityrosine in skeletal muscle. In contrast, antioxidant therapy or exercise training minimally affected o-tyrosine levels in this tissue. Levels of the oxidized amino acids in urine samples mirrored those of skeletal muscle proteins. Quantification of the levels of oxidized amino acids in urine may thus serve as a noninvasive measure of oxidative stress in vivo because they change in parallel with levels of protein-bound oxidized amino acids in skeletal muscle.
Leptin deficiency enhances sensitivity to endotoxin-induced lethality
Authors: Faggioni Raffaella , Fantuzzi Giamila , Gabay Cem , Moser Arthur , Dinarello Charles A. , Feingold Kenneth R. , Grunfeld Carl
Published: December 2017

Leptin is induced by lipopolysaccharide (LPS) and cytokines. We investigated the role of leptin in LPS-induced toxicity using leptin-deficient ( ob/ ob) and leptin receptor-deficient ( db/ db) mice. Sensitivity to LPS-induced mortality is significantly greater in ob/ obmice compared with their own lean littermates but not in db/ dbmice. LPS reduced serum glucose in both ob/ oband db/ dbmice but induced corticosterone only in db/ dbmice. Despite the very high basal levels of serum leptin in db/ dbmice, a twofold increase in serum leptin levels was observed after LPS in both db/ dbmice and their lean littermates. No differences were detected in LPS-induced serum levels of interleukin (IL)-1β, tumor necrosis factor, macrophage inflammatory protein-1α, and interferon-γ in ob/ obmice compared with their own littermates. In contrast, a blunted induction of IL-10 and IL-1 receptor antagonist (IL-1Ra) was observed in ob/ obmice compared with their littermates. In vitro, leptin induced IL-1Ra production and upregulated the IL-1Ra induction by LPS in macrophages. Moreover, treatment with leptin reversed the increased sensitivity to LPS-induced lethality found in ob/ obmice. These results suggest that leptin participates in the host response to inflammation by modulating the host immune and cytokine responses after LPS.