bluuebunny/crossref_metadata_2025 huggingface dataset:
Regulation of androgen receptor expression at the onset of functional overload in rat plantaris muscle
Authors: Lee Won Jun , Thompson Raymond W. , McClung Joseph M. , Carson James A.
Published: March 2015

Skeletal muscle androgen receptor (AR) expression at the onset of functional overload (OV) has not been well described. It is also not known if overload and/or anabolic steroid differentially regulate AR expression. The purpose of this study was to examine AR gene expression at the onset of functional OV in rat plantaris muscle with and without nandrolone decanoate (ND) administration. The functional significance of AR protein induction was examined using skeletal α-actin promoter activity in transiently transfected CV-1 fibroblast cells. Male Sprague-Dawley rats (∼125 g) were functionally overloaded for 1, 3, 7, or 21 days. A subset of animals was given an ND (6 mg/kg) injection at day 0 and then overloaded for 3 days. Control animals underwent sham surgeries. AR protein concentration increased 106 and 279% after 7 and 21 days of OV, respectively. AR mRNA increased 430% after 7 days of OV. AR protein expression in C2C12 murine myotubes subjected to 1% chronic radial stretch for 18 h was elevated 101% compared with control. ND treatment increased AR protein concentration 1,300% compared with controls, and there was no additional effect when ND and OV were combined. ND with 3 days of OV treatment increased AR mRNA expression 50% compared with control. AR overexpression in transiently transfected CV-1 fibroblast cells increased -424 bp skeletal α-actin promoter activity 80 to 1,800% in a dose-dependent fashion. Co-overexpression of either serum response factor (SRF) or active RhoA with AR overexpression induced a synergistic 36- and 28-fold induction of skeletal α-actin promoter. Cotransfection of AR, SRF, and active RhoA induced 180-fold increase in skeletal α-actin promoter activity. In conclusion, AR protein expression is increased after 7 days of functional OV, and this induction is regulated pretranslationally. AR induction in conjunction with SRF and RhoA signaling may be an important regulator of gene expression during overload-induced muscle growth.
No evidence for HPA reset in adult sheep with high blood pressure due to short prenatal exposure to dexamethasone
Authors: Dodic Miodrag , Peers Arianne , Moritz Karen , Hantzis Vicky , Wintour E. Marelyn
Published: March 2015

Exposure of pregnant ewes to dexamethasone, for only 2 days (term ∼150 days) at 27 days of gestation ( group D), results in adult offspring with high blood pressure. In this study, hemorrhage stress has been used to see whether in these animals the responsiveness of the hypothalamo-pituitary-adrenal (HPA) axis is altered. In addition, we studied mineralocorticoid (MR) and glucocorticoid (GR) receptor gene expression in the hippocampus and GR gene expression in the hypothalamus using real-time PCR. Calculated areas under the adrenocorticotropin, arginine vasopressin, and cortisol plasma concentration curves in response to hemorrhage were similar between the control and group D. In addition, there was no significant difference in the expression of MR and GR in the hippocampus or GR in the hypothalamus between the control and group D. Taken together, it is unlikely that reset in the HPA axis plays a major role in this particular model of “programmed” hypertension.
Effect of mild carboxy-hemoglobin on exercising skeletal muscle: intravascular and intracellular evidence
Authors: Richardson R. S. , Noyszewski E. A. , Saltin B. , González-Alonso J.
Published: March 2015

We studied muscle blood flow, muscle oxygen uptake (V˙o 2), net muscle CO uptake, Mb saturation, and intracellular bioenergetics during incremental single leg knee-extensor exercise in five healthy young subjects in conditions of normoxia, hypoxia (H; 11% O2), normoxia + CO (COnorm), and 100% O2+ CO (COhyper). Maximum work rates and maximal oxygen uptake (V˙o 2 max) were equally reduced by ≈14% in H, COnorm, and COhyper. The reduction in arterial oxygen content (CaO2 ) (≈20%) resulted in an elevated blood flow (Q) in the CO and H trials. Net muscle CO uptake was attenuated in the CO trials. Suprasystolic cuff measurements of the deoxy-Mb signal were not different in terms of the rate of signal rise or maximum signal attained with and without CO. At maximal exercise, calculated mean capillary Po 2 was most reduced in H and resulted in the lowest Mb-associated Po 2. Reductions in ATP, PCr, and pH during H, COnorm, and COhyper occurred earlier during progressive exercise than in normoxia. Thus the effects of reduced CaO2 due to mild CO poisoning are similar to H.
A nonlinear compartmental model of Sr metabolism. II. Its physiological relevance for Ca metabolism
Authors: Staub J. F. , Foos E. , Courtin B. , Jochemsen R. , Perault-Staub A. M.
Published: March 2015

We have studied the peculiarities of the nonlinear compartmental model for human Sr metabolism (Staub JF, Foos E, Courtin B, Jochemsen R, and Perault-Staub AM. Am J Physiol Regul Integr Comp Physiol 284: R819–R834, 2003), including its physiological reliability in the context of Sr-Ca similarity-dissimilarity. We found it to be relevant to Ca metabolism, except for discrimination against Sr relative to Ca at urinary and intestinal levels. The main findings are as follows: 1) the saturable part of intestinal absorption, shared by Sr and Ca, does not seem to be responsible for the discrimination of the transcellular pathway; 2) although there is little discrimination in bone, the physicochemical behaviors of Sr and Ca at the bone surface differ, at least quantitatively; and 3) Sr behaves as a “tracer” for Ca metabolic pathways and, under non-steady-state conditions, can also reveal self-regulatory processes. It is suggested that they depend on Ca2+(cationic)-sensing receptors that are apparently more sensitive to Sr than to Ca. Acting on gastrointestinal and osteoblast lineage cells, these slow processes might contribute to adaptive, rather than homeostatic, regulation of Ca metabolism. Understanding these features could help clarify the pharmacological and therapeutic effects of oral Sr.
Seasonal dynamics of flight muscle fatty acid binding protein and catabolic enzymes in a migratory shorebird
Authors: Guglielmo Christopher G. , Haunerland Norbert H. , Hochachka Peter W. , Williams Tony D.
Published: March 2015

We developed an ELISA to measure heart-type fatty acid binding protein (H-FABP) in muscles of the western sandpiper ( Calidris mauri), a long-distance migrant shorebird. H-FABP accounted for almost 11% of cytosolic protein in the heart. Pectoralis H-FABP levels were highest during migration (10%) and declined to 6% in tropically wintering female sandpipers. Premigratory birds increased body fat, but not pectoralis H-FABP, indicating that endurance flight training may be required to stimulate H-FABP expression. Juveniles making their first migration had lower pectoralis H-FABP than adults, further supporting a role for flight training. Aerobic capacity, measured by citrate synthase activity, and fatty acid oxidation capacity, measured by 3-hydroxyacyl-CoA-dehydrogenase and carnitine palmitoyl transferase activities, did not change during premigration but increased during migration by 6, 12, and 13%, respectively. The greater relative induction of H-FABP (+70%) with migration than of catabolic enzymes suggests that elevated H-FABP is related to the enhancement of uptake of fatty acids from the circulation. Citrate synthase, 3-hydroxyacyl-CoA-dehydrogenase, and carnitine palmitoyl transferase were positively correlated within individuals, suggesting coexpression, but enzyme activities were unrelated to H-FABP levels.
Cholecystokinin and stomach distension combine to reduce food intake in humans
Authors: Kissileff Harry R. , Carretta Julie C. , Geliebter Allan , Pi-Sunyer F. Xavier
Published: March 2015

The aim of this study was to test the hypothesis that gastric distension can enhance the effect of cholecystokinin (CCK) on reduction of food intake in men and women. Eight normal-weight subjects of each gender were tested four times each with either CCK or saline infusion crossed with gastric distension or no distension. Intravenous infusion of a low dose of CCK octapeptide (CCK-8; 112 ng/min for 23 min) combined with a subthreshold gastric distension induced by a water-filled balloon (300 ml) resulted in a significant (means ± SED: 191 ± 61 g in men, 209 ± 61 g in women, and 200 ± 43 g combined) reduction in intake of a liquid meal compared with saline infusion and unfilled gastric balloon. This combined effect was the result of a large and significant CCK effect when the stomach was distended (CCK vs. saline with distension: 169 ± 43 g) and a small and insignificant distension effect (distension vs. no distension without CCK: 31 ± 43 g). The CCK effect alone on intake (CCK vs. saline) without distension was not significant in men (72 ± 61 g) but was significant in women (121 ± 61 g). These results are consistent with the hypothesis that CCK's suppression of food intake is enhanced when the stomach is distended.
Accelerated recovery after endotoxic challenge in heat shock-pretreated mice
Authors: Paidas Charles N. , Mooney Maria Lourdes , Theodorakis Nicholas G. , De Maio Antonio
Published: March 2015

The inflammatory response induced by bacterial lipopolysaccharide (LPS) has profound metabolic and physiological effects. Thus hepatic glucose production is depressed after LPS administration, which is, at least in part, due to the downregulation of phospho enolpyruvate carboxykinase (PEPCK) expression. PEPCK is a key regulatory enzyme of the gluconeogenic pathway. Expression of heat shock proteins (hsps) is a well-conserved response to stress correlated with protection from subsequent insults including inflammation. In this study, the expression of PEPCK was observed to be preserved after injection of LPS in heat shock-pretreated mice. Protection of PEPCK expression was limited to the time after heat shock treatment that displayed hsp70. Comparison of the transcription rate and mRNA levels of PEPCK after LPS injection between mice that were heat shock pretreated or not indicated that the preservation of PEPCK expression was not due to initial protection from the LPS challenge. On the contrary, it was mediated by a rapid recovery after the LPS insult at the level of transcription. These observations suggest that the mechanism of heat shock-mediated protection (stress tolerance) after LPS challenge is due to an increase in the capacity of the organism to recover rather than deterrence from the insult.
Magnetic fields and the melatonin hypothesis: a study of workers chronically exposed to 50-Hz magnetic fields
Authors: Touitou Yvan , Lambrozo Jacques , Camus Françoise , Charbuy Henriette
Published: March 2015

Because epidemiological studies report clinical disorders (mainly neurobehavioral alterations and/or cancer) that may be related to diminished melatonin secretion or to changes in its circadian rhythm in subjects living or working in environments exposed to magnetic fields, research on the effects of these fields in humans is particularly important. In this study, we examine the circadian rhythm of melatonin in 15 men exposed chronically and daily for a period of 1–20 yr, in the workplace and at home, to a 50-Hz magnetic field in search of any cumulative effect from those chronic conditions of exposure. The weekly geometric mean of individual exposures ranged from 0.1 to 2.6 μT. The results are compared with those for 15 unexposed men who served as controls (individual exposures ranged from 0.004 to 0.092 μT). Blood samples were taken hourly from 2000 to 0800. Nighttime urine was also collected and analyzed. This work shows that subjects exposed over a long period (up to 20 yr) and on a daily basis to magnetic fields experienced no changes in their plasma melatonin level, their urinary 6-sulfatoxymelatonin level, or the circadian rhythm of melatonin. Our data strongly suggest that magnetic fields do not have cumulative effects on melatonin secretion in humans and thus clearly rebut the “melatonin hypothesis” that a decrease in plasma melatonin concentration (or a disruption in its secretion) explains the occurrence of clinical disorders or cancers possibly related to magnetic fields.
Thermoregulation in rats during early postnatal maturation: importance of nitric oxide
Authors: Malik Sulleman S. , Fewell James E.
Published: March 2015

Experiments were carried out to determine the role of nitric oxide in mediating autonomic and behavioral thermoregulatory control in rat pups on postnatal days 1-2, 5-6, and 10-11. For an experiment, each pup received a subcutaneous injection of vehicle, NG-nitro-d-arginine methyl ester (d-NAME; 100 mg/kg), or NG-nitro-l-arginine methyl ester (l-NAME; 100 mg/kg) before being placed in a metabolic chamber or in a thermocline with a linear temperature gradient of 23 to 43°C. In the metabolic chamber, oxygen consumption and core temperature were measured as ambient temperature was decreased from 40 to 15°C over a 60-min period. Decreasing ambient temperature elicited an increase in oxygen consumption in all age groups that received vehicle or d-NAME. The lower critical temperature and peak oxygen consumption upon exposure to cold after vehicle were 41 ± 10 ml · kg-1 · min-1 at 30°C, 43 ± 12 ml · kg-1 · min-1 at 28°C, and 55 ± 11 ml · kg-1 · min-1 at 25°C in the 1- to 2-, 5- to 6-, and 10- to 11-day-old pups, respectively. Administration of l-NAME abolished the oxygen consumption response to cold in the 1- to 2- and 5- to 6-day-old pups and significantly attenuated the oxygen consumption response to cold in the 10- to 11-day-old pups. Selected ambient temperature in the thermocline was not significantly affected by prior administration of d-NAME or l-NAME compared with vehicle. Thus our data provide evidence that the nitric oxide system plays a role in mediating autonomic but not behavioral thermoregulatory control in rat pups during early postnatal maturation.
Role of spinal NMDA and non-NMDA receptors in the pressor reflex response to abdominal ischemia
Authors: Gee B. Y. , Tjen-A-Looi S. C. , Hill J. M. , Chahal P. S. , Longhurst J. C.
Published: March 2015

Abdominal ischemia induces a pressor reflex caused mainly by C-fiber afferent stimulation. Because excitatory amino acids, such as glutamate, bind to N-methyl-d-aspartate (NMDA) and non-NMDA [ dl-α-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA)] receptors and serve as important spinal neurotransmitters, we hypothesized that both receptors play a role in the abdominal ischemia pressor reflex. In chloralose-anesthetized cats, NMDA receptor blockade with 25.0 mM dl-2-amino-5-phosphonopentanoate did not alter the pressor reflex (33 ± 9 to 33 ± 7 mmHg, P > 0.05, n = 4), whereas AMPA receptor blockade with 4.0 mM 6-nitro-7-sulfamylbenzo( f)quinoxaline-2,3-dione significantly attenuated the reflex (29 ± 5 to 16 ± 4 mmHg, P < 0.05, n = 6). Because several studies suggest that anesthesia masks the effects of glutamatergic receptors, this experiment was repeated on decerebrate cats, and in this group, NMDA receptor blockade with 25.0 mM dl-2-amino-5-phosphonopentanoate significantly altered the pressor reflex (36 ± 3 to 25 ± 4 mmHg, P < 0.05, n = 5). Our combined data suggest that spinal NMDA and AMPA receptors play a role in the abdominal ischemia pressor reflex.
Temperature dependence of gonadal regression in Syrian hamsters exposed to short day lengths
Authors: Larkin Jennie E. , Jones Jennifer , Zucker Irving
Published: March 2015

We sought to determine whether ambient temperature (Ta) affects gonadal function by altering the rate at which circadian rhythms entrain to short day lengths. Syrian hamsters were housed in cages where they received 14 h of light per day (“long days,” 14L) at 22°C. Hamsters were then transferred to cages to receive 10 h of light per day (“short days,” 10L) and kept at 5, 22, or 28°C or were maintained in 14L at 22°C. Body mass and estimated testis volume as well as duration of nocturnal locomotor activity (α), previously established as a reliable indicator of the duration of nocturnal melatonin secretion, were determined over the course of 24 wk. Testicular regression in short days was accelerated by 4 wk at 5°C and delayed by 3 wk at 28°C relative to 22°C. The interval between α-expansion and initiation of testicular regression was markedly affected by Ta with delays of 0, 3, and 6 wk at 5, 22, and 28°C, respectively. All hamsters held at 5 and 22°C underwent testicular regression, but 25% of those maintained at 28°C failed to do so. We suggest that Ta modulates testicular regression primarily by affecting responsiveness of neuroendocrine target tissues to long melatonin signals.
Xenobiotic efflux pumps in isolated fish brain capillaries
Authors: Miller David S. , Graeff Claudia , Droulle Lucy , Fricker Stefanie , Fricker Gert
Published: March 2015

To identify specific transporters that drive xenobiotics from the central nervous system to blood, the accumulation of fluorescent drugs was studied in isolated capillaries from killifish and dogfish shark brain using confocal microscopy and quantitative image analysis. In killifish brain capillaries, luminal accumulation of fluorescent derivatives of cyclosporin A and verapamil was concentrative, specific, and energy dependent (inhibition by KCN). Transport was reduced by PSC-833, but not by leukotriene C4, indicating the involvement of P-glycoprotein. The ability of capillaries to transport the cyclosporin A derivative was unchanged over 20 h, demonstrating the long-term viability of the preparation. Luminal accumulation of the fluorescent organic anions sulforhodamine 101 and fluorescein-methotrexate was also concentrative, specific, and energy dependent. Transport of these compounds was reduced by leukotriene C4, but not by PSC-833, indicating the involvement of a multidrug resistance-associated protein (Mrp). Similar results were obtained for isolated capillaries from dogfish shark. Immunostaining localized P-glycoprotein and Mrp2 to the luminal surface of the killifish brain capillary endothelium. These findings validate a new and long-lived comparative model for studying drug transport across the blood-brain barrier and, as in mammals, implicate P-glycoprotein and Mrp2 in transport from the central nervous system to blood in fish.
Citrulline is not the major product using the standard “NOS activity” assay on renal cortical homogenates
Authors: Conrad Kirk P. , Powers Robert W. , Davis Alan K. , Novak Jackie
Published: March 2015

A standard approach to assessing nitric oxide synthase (NOS) activity in tissue homogenates is 1) removal of small-molecular-weight substances by size-exclusion chromatography, 2) adding back of substrates/cofactors in precise concentrations with a radioactive isotope of arginine (Arg), and 3) quantification of labeled citrulline (Cit) after separation of Arg and Cit by cation-exchange column chromatography. Using this approach andl-[2,3-3H]Arg, we found that the major product(s) was not Cit in cortical homogenates prepared from rat, mouse, and human kidneys. The product(s) mimicked Cit, insofar as it passed freely through cation-exchange columns and comigrated with Cit on both one-dimensional and two-dimensional straight-phase thin-layer chromatography systems. However, it was clearly resolved from Cit by precolumn derivatization and reverse-phase HPLC. The maximum velocity and Michaelis-Menten constant were approximately 100 pmol · mg protein−1· min−1and 100 μM, respectively, in renal cortical homogenates from rats. The enzyme activity was the same in the presence or absence of cofactors including Ca2+, calmodulin, tetrahydrobiopterin, and NADPH. It was only modestly inhibited by l-Arg analogs and was mainly in the supernatant after a 100,000 g centrifugation. These enzyme characteristics contrasted markedly with those simultaneously obtained for NOS activity in placental homogenates. Thus results from the conventional NOS activity assay should be viewed cautiously.
Effect of insulin and growth hormone on plasma leptin in periparturient dairy cows
Authors: Leury Brian J. , Baumgard Lance H. , Block Stephanie S. , Segoale Nthabisheng , Ehrhardt Richard A. , Rhoads Robert P. , Bauman Dale E. , Bell Alan W. , Boisclair Yves R.
Published: March 2015

After parturition, dairy cows suffer from an intense energy deficit caused by the onset of copious milk secretion and an inadequate increase in voluntary food intake. We previously showed that this energy deficit contributes to a decline in plasma leptin. This decline mirrors that of plasma insulin but is reciprocal to the profile of plasma growth hormone (GH), suggesting that both hormones may regulate plasma leptin in periparturient dairy cows. To study the role of insulin, hyperinsulinemic-euglycemic clamps were performed on six dairy cows in late pregnancy (LP, 31 days prepartum) and early lactation (EL, 7 days postpartum). Infusion of insulin (1 μg·kg body wt-1·h-1) caused a progressive rise in the plasma concentration of leptin that reached maximum levels at 24 h during both physiological states. At steady states, the absolute increase in plasma leptin was greater in LP than in EL cows (2.4 vs. 0.4 ng/ml). Insulin infusion increased leptin mRNA in adipose tissue during LP but not during EL. During lactation, mammary epithelial cells expressed leptin mRNA but insulin did not increase milk leptin output. In contrast, a 3-day period of GH administration had no effect on plasma leptin during LP or EL. Therefore, insulin increases plasma leptin in LP by stimulating adipose tissue synthesis but has only marginal effects in EL, when cows are in negative energy balance. Other factors, such as increased response of adipose tissue to β-adrenergic signals, probably contribute to the reduction of plasma leptin in early lactating dairy cows.
A neurochemical mechanism for hypoxia-induced anapyrexia
Authors: Steiner Alexandre A. , Rocha Maria J. A. , Branco Luiz G. S.
Published: March 2015

Hypoxia evokes a regulated decrease in body temperature, a response that has been termed anapyrexia, but the mechanisms involved are poorly understood. Therefore, the present study was undertaken to test the hypothesis that hypoxia-induced anapyrexia results from the activation of cAMP- and cGMP-dependent pathways in the preoptic region (PO). Adult male Wistar rats weighing 230–260 g were used. Body temperature was monitored by biotelemetry, and the levels of cAMP and cGMP were determined in the anteroventral third ventricular region (AV3V), where the PO is located. Using immunohistochemistry, we observed that the PO contains a high density of cAMP- and cGMP-containing cells. Interestingly, hypoxia exposure raised the levels of cAMP and cGMP in the AV3V. Intra-PO microinjection of Rp-cAMPS, an inhibitor of cAMP-dependent protein kinase, attenuated hypoxia-induced anapyrexia. Similarly, intra-PO microinjection of the mixed β-adrenoceptor/serotonin (5-HT1A) receptor antagonist propranolol also impaired the drop in body temperature in response to hypoxia. The reduction in body temperature evoked by intra-PO serotonin, but not epinephrine, was blocked by Rp-cAMPS, indicating the involvement of a preoptic serotonin-cAMP pathway in the development of anapyrexia. Moreover, microinjection of NG-monomethyl-l-arginine, an inhibitor of nitric oxide (NO) synthesis, or Rp-cGMPS, an inhibitor of cGMP-dependent protein kinase, into the PO also attenuated hypoxia-induced anapyrexia. In conclusion, the present study supports that hypoxia-induced anapyrexia results from the activation of the serotonin-cAMP and NO-cGMP pathways in the PO.
Decrease of food intake by MC4-R agonist MTII in Siberian hamsters in long and short photoperiods
Authors: Schuhler Sandrine , Horan Tracey L. , Hastings Michael H. , Mercer Julian G. , Morgan Peter J. , Ebling Francis J. P.
Published: March 2015

We investigated the role of the hypothalamic melanocortin system in the regulation of food intake in the Siberian hamster, which shows a profound seasonal decrease in food intake and body weight in short photoperiod (SP). In male hamsters maintained in long photoperiod (LP), intracerebroventricular injection of melanotan II (MTII) just before lights off significantly decreased food intake relative to vehicle treatment over the 6-h observation period. Similar effects were observed in age-matched hamsters after exposure to a short daylength for 9 wk, when body weight had significantly decreased. There was no clear difference in either the magnitude of response or the dose required for half-maximal inhibition of food intake in hamsters in SP compared with those in LP. MTII significantly increased grooming in both LP and SP. Our results indicate that the melanocortin system is a potent short-term regulator of food intake. However, the lack of differential response or sensitivity to MTII treatment in the obese (LP) vs. lean (SP) states does not support the hypothesis that changes in this melanocortin pathway underlie the long-term decrease in food intake that occurs in this seasonal model.
Impaired responsiveness of renal mechanosensory nerves in heart failure: role of endogenous angiotensin
Authors: Kopp Ulla C. , Cicha Michael Z. , Smith Lori A.
Published: March 2015

Increasing renal pelvic pressure results in PGE2-mediated release of substance P. Substance P increases afferent renal nerve activity (ARNA), which leads to a reflex increase in urinary sodium excretion (UNaV). Endogenous ANG II modulates the responsiveness of renal mechanosensory nerves. The ARNA and UNaV responses are suppressed by low- and enhanced by high-sodium diet. We examined whether the ARNA responses are altered in rats with congestive heart failure (CHF), a condition characterized by increased ANG II and sodium retention. The ARNA responses to increasing renal pelvic pressure ≤7.5 mmHg were suppressed in CHF vs. sham-CHF rats fed normal sodium diet. In CHF rats, increasing renal pelvic pressure 2.5 and 7.5 mmHg increased ARNA 0 ± 1 and 13 ± 2% ( P < 0.01) before and 9 ± 1 ( P < 0.01) and 19 ± 1% ( P < 0.01) during renal pelvic perfusion with losartan. Losartan had no effect on the ARNA responses in sham-CHF rats. In isolated renal pelvises from CHF rats, PGE2increased substance P release from 11 ± 2 to 15 ± 3 pg/min (not significant) without and from 16 ± 2 to 30 ± 4 pg/min ( P < 0.01) with losartan in the incubation bath. Losartan had no effect on PGE2-mediated substance P release in sham-CHF rats. In conclusion, the responsiveness of renal mechanosensory nerves is impaired in CHF rats due to ANG II inhibiting PGE2-mediated release of substance P from renal pelvic nerves.
Cyclooxygenase-2 contributes to elevated renin in the early postnatal period in rats
Authors: Stubbe Jane , Jensen Boye L. , Bachmann Sebastian , Morsing Peter , Skøtt Ole
Published: March 2015

We asked whether cyclooxygenase (COX) activity controls the renin-angiotensin system in the postnatal period. During kidney development, renin peaked at postnatal days 0–1 at the mRNA, tissue protein [renal renin concentration (RRC)], and plasma renin concentration (PRC) levels and was widely expressed along preglomerular vessels. PRC and renin mRNA expression was elevated until weaning in the 4th postnatal week compared with adult rats. Renocortical COX-2 was restricted to Tamm-Horsfall protein-positive cells in the thick ascending limb of Henle's loop, and cortical COX-2 mRNA and protein expression were elevated along with PRC in the 2nd and 3rd postnatal weeks. In contrast, cortical COX-1 expression was constant, but medullary COX-1 expression increased eightfold from the 1st to 4th postnatal week. A COX-2-selective blocker, parecoxib, and a nonselective blocker, indomethacin, given in a period with COX-2 induction from postnatal day 6 to day 12, markedly decreased PRC, but not renin mRNA or RRC. Inhibition of angiotensin AT1receptors by candesartan from postnatal day 1 to day 5increased COX-2 mRNA (2.5-fold), protein, and distribution, renin mRNA (7-fold) and PRC (20- to 70-fold), but had no influence on COX-1 mRNA. Thus, due to very low levels of expression, COX-2 is unlikely to be responsible for the birth peak of renin, but COX-2 activity supports renin secretion later in the suckling period. ANG II negatively feeds back on renocortical COX-2 expression in the 1st postnatal days with high activity of the renin system. We suggest that suckling in the rat is correlated to an enhanced, COX-2-mediated, secretory activity of renin-producing juxtaglomerular cells.
Isolation and characterization of mitochondria-rich cell types from the gill of freshwater rainbow trout
Authors: Galvez Fernando , Reid Scott D. , Hawkings Guy , Goss Greg G.
Published: March 2015

A magnetic cell separation technique (MACS) was developed for isolating and characterizing peanut lectin agglutinin positive (PNA+) cells from rainbow trout gills. Percoll density separated mitochondria-rich (MR) cells were serially labeled with PNA-FITC and an anti-FITC antibody covalently coupled to a 50-nm iron particle and then applied to a magnetic column. PNA+MR cells were enriched to >95% purity. Transmission electron microscopy analysis of both the PNA+and PNA negative (PNA−) fraction showed that PNA binds to MR chloride cells while the PNA−cell fraction is comprised of MR cells with features characteristic of pavement cells. Western blotting demonstrated that both PNA+and PNA−fractions had high levels of Na+-K+-ATPase and Sco1 expression; however, relative expression of H+-ATPase in PNA+and PNA−cells demonstrated that untreated fish had twofold higher H+-ATPase levels in PNA−cells relative to the PNA+cells. Furthermore, hypercapnic acidosis significantly increased the relative H+-ATPase expression on PNA−cells only, whereas metabolic alkalosis had no significant effect.
Electrophysiological properties of rainbow trout cardiac myocytes in serum-free primary culture
Authors: Nurmi Antti , Vornanen Matti
Published: March 2015

A low-density primary culture of trout ventricular myocytes in serum-free growth medium was established and maintained for up to 10 days at 17°C. The myocytes retained their normal rod shaped morphology, capacitive surface area of the sarcolemma (SL), and contractile quiescence. However, sarcolemmal cation currents changed significantly, some permanently, some transiently, after 8–10 days of culture. TTX-sensitive sodium current ( INa) and Ba2+-sensitive background inward rectifier potassium current ( IK1) were permanently depressed to 24–28% of their control density measured in freshly isolated myocytes. In contrast, L-type calcium current ( ICa) was only transiently downregulated; after 2–3 days in culture, the density of the current was 32% of the control and recovered to the control value after 8–10 days in culture. The changes in membrane currents were reflected in the shape of the action potential (AP). After 2–3 days in culture, maximal overshoot potential and resting potential were significantly reduced, and the durations of the AP at 50 and 90% repolarization were significantly increased. These changes became significantly more pronounced after 8–10 days of culture, with the exception of AP duration at 50% repolarization level. The shortening of the early plateau phase may reflect an additional change to an outward current, presumably the rapid component of the delayed rectifier ( IKr). Although the present findings indicate that fish cardiac myocytes can be maintained in serum-free primary culture for at least 10 days at 17°C, some but not all of the electrophysiological characteristics of the myocytes change markedly during culture. The changes in ion currents were not due to loss of sarcolemmal membrane and therefore are likely to represent altered expression of cation currents as an adaptive response to culture conditions.
Inhibiting adenosine deaminase modulates the systemic inflammatory response syndrome in endotoxemia and sepsis
Authors: Adanin Simon , Yalovetskiy Igor V. , Nardulli Beth A. , Sam Albert D. , Jonjev Živojin S. , Law William R.
Published: March 2015

By pharmacological manipulation of endogenous adenosine, using chemically distinct methods, we tested the hypothesis that endogenous adenosine tempers proinflammatory cytokine responses and oxyradical-mediated tissue damage during endotoxemia and sepsis. Rats were pretreated with varying doses of pentostatin (PNT; adenosine deaminase inhibitor) or 8-sulfophenyltheophylline (8-SPT; adenosine receptor antagonist) and then received either E. coli endotoxin (lipopolysaccharide; 0.01 or 2.0 mg/kg) or a slurry of cecal matter in 5% dextrose in water (200 mg/kg). Resultant levels of tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-10 were measured in serum and in liver and spleen. Untreated, 2 mg/kg lipopolysaccharide elevated serum TNF-α, IL-1β, and IL-10. PNT dose dependently attenuated, without ablating, the elevation in serum TNF-α and IL-1β and raised liver and spleen IL-10. PNT also attenuated elevation of TNF-α in serum, liver, and spleen at 4 and 24 h after sepsis induction, and 8-SPT resulted in higher proinflammatory cytokines. Modulating endogenous adenosine was also effective in exacerbated (8-SPT) or diminished (PNT) tissue peroxidation. Survival from sepsis was also improved when PNT was used as a posttreatment. These data indicate that endogenous adenosine is an important modulatory component of systemic inflammatory response syndromes. These data also indicate that inhibition of adenosine deaminase may be a novel and viable therapeutic approach to managing the systemic inflammatory response syndrome without ablating important physiological functions.
Mating behavior is controlled by acute changes in metabolic fuels
Authors: Temple Jennifer L. , Schneider Jill E. , Scott Deanna K. , Korutz Alexander , Rissman Emilie F.
Published: March 2015

Mild food restriction for 48 h inhibits mating behavior in female musk shrews ( Suncus murinus). However, mating behavior is restored after a 90-min feeding bout. In this series of experiments, we examined the role of metabolic fuels in this behavioral restoration. First, drugs reported to block glycolysis or fatty acid oxidation were given 2 h before mating. Both treatments inhibited mating in food-restricted females that were refed after treatment. Blood glucose levels were assessed in females that were fed ad libitum, food restricted, or food restricted and refed for 90 min. Food restriction significantly lowered blood glucose compared with ad libitum feeding or food restriction in combination with 90 min of refeeding. However, neither glucose nor fat alone could substitute for food and promote mating behavior in food-restricted females. In addition, analysis of ketone bodies and body composition in females demonstrated low or undetectable levels of these energy substrates. Our data suggest that musk shrews have relatively little stored energy. Therefore, female musk shrews rely on continuous food intake and monitor multiple cues acutely, including glucose availability and fatty acid oxidation. This ensures that mating does not occur when adequate energy is unavailable.
Vasodilator responses to adenosine and hyperemia are mediated by A1and A2receptors in the cat vascular bed
Authors: Bivalacqua Trinity J. , Champion Hunter C. , Lambert David G. , Kadowitz Philip J.
Published: March 2015

Hemodynamic responses to adenosine, the A1receptor agonists N6-cyclopentyladenosine (CPA) and adenosine amine congener (ADAC), and the A2receptor agonist 5′-( N-cyclopropyl)-carboxamido-adenosine (CPCA) were investigated in the hindquarter vascular bed of the cat under constant-flow conditions. Injections of adenosine, CPA, ADAC, CPCA, ATP, and adenosine 5′- O-(3-thiotriphosphate) (ATPγS) into the perfusion circuit induced dose-related decreases in perfusion pressure. Vasodilator responses to the A1agonists were reduced by the A1receptor antagonists KW-3902 and CGS-15943, whereas responses to CPCA were reduced by the A2antagonist KF-17837. Vasodilator responses to adenosine were reduced by KW-3902, CGS-15943, and by KF-17837, suggesting a role for both A1and A2receptors. Vasodilator responses to ATP and the nonhydrolyzable ATP analog ATPγS were not attenuated by CGS-15943 or KF-17837. After treatment with the nitric oxide synthase inhibitor Nω-nitro-l-arginine methyl ester, the cyclooxygenase inhibitor sodium meclofenamate, or the ATP-dependent K+(K[Formula: see text]) channel antagonists U-37883A or glibenclamide, responses to adenosine and ATP were not altered. Responses to adenosine, CPA, and CPCA were increased in duration by rolipram, a type 4 cAMP phosphodiesterase inhibitor, but were not altered by zaprinast, a type 5 cGMP phosphodiesterase inhibitor. When blood flow was interrupted for a 30-s period, the magnitude and duration of the reactive vasodilator response were reduced by A1and A2receptor antagonists. These data suggest that vasodilator responses to adenosine and the A1and A2agonists studied are not dependent on the release of cyclooxygenase products, nitric oxide, or the opening of K[Formula: see text] channels in the regional vascular bed of the cat. The present data suggest a role for cAMP in mediating responses to adenosine and suggest that vasodilator responses to adenosine and to reactive hyperemia are mediated in part by A1and A2receptors in the hindquarter vascular bed of the cat.
Intraventricular melanin-concentrating hormone stimulates water intake independent of food intake
Authors: Clegg Deborah J. , Air Ellen L. , Benoit Stephen C. , Sakai Randall S. , Seeley Randy J. , Woods Stephen C.
Published: March 2015

The lateral hypothalamus (LH) has a critical role in the control of feeding and drinking. Melanin-concentrating hormone (MCH) is an orexigenic peptidergic neurotransmitter produced primarily in the LH, and agouti-related protein (AgRP) is an orexigenic peptidergic neurotransmitter produced exclusively in the arcuate (ARC), an area that innervates the LH. We assessed drinking and eating after third ventricular (i3vt) administration of MCH and AgRP. MCH (2.5, 5, and 10 μg i3vt) significantly increased food as well as water intake over 4 h when administered during either the light or the dark portion of the day-night cycle. When MCH (5 μg) was administered to rats with access to water but no food, they drank significantly more water than when given the vehicle. AgRP (7 μg i3vt), on the other hand, increased water intake but only in proportion to food intake during the dark and the light, and water intake was not increased after i3vt AgRP in the absence of food. Hence, in contrast to AgRP, MCH elicits increased water intake independent of food intake. These results are consistent with historical data linking activity of the LH with water as well as food intake.
β-Adrenoceptor control of G protein function in the neonate: determinant of desensitization or sensitization
Authors: Auman J. T. , Seidler F. J. , Slotkin T. A.
Published: March 2015

Neonatal β-adrenoceptors (β-ARs) are resistant to agonist-induced desensitization. We examined the functioning of Giand Gsafter repeated administration of β-AR agonists to newborn rats. Isoproterenol (β1/β2agonist) obtunded Gifunction in the heart but not the liver; in contrast, terbutaline, a β2-selective agonist, enhanced Gifunction. Isoproterenol, but not terbutaline, increased membrane-associated Gsα, which would enhance receptor function. In addition, isoproterenol increased and terbutaline maintained the proportion of the short-splice (S) variant of Gsαin the membrane fraction; GsαS is functionally more active than the long-splice variant. Either isoproterenol or terbutaline treatment increased Gsαin the cytosolic fraction, a characteristic usually associated with desensitization in the adult. Decreased Giactivity, coupled with increased membrane-associated Gsαconcentrations and maintenance or increases in membrane GsαS, provide strong evidence that unique effects on G protein function underlie the ability of the immature organism to sustain β-AR cell signaling in the face of excessive or prolonged stimulation; these mechanisms also contribute to tissue selectivity of the effects of β-agonists with divergent potencies toward different β-AR subtypes.
Relative contribution of the TNF-α receptors to murine intimal hyperplasia
Authors: Zimmerman Michael A. , Reznikov Leonid L. , Sorensen Amy C. , Selzman Craig H.
Published: March 2015

Tumor necrosis factor-α (TNF-α) is an important mediator in the inflammatory response to vascular injury. The present study sought to determine the relative contribution of each TNF-α receptor subtype (p55 and p75) to intimal hyperplasia (IH) and characterize the mechanisms of transcriptional regulation after vascular injury. A murine model of wire carotid arterial injury was employed to induce IH in wild-type (WT), p55-deficient (p55−/−), and p75-deficient (p75−/−) mice. Compared with injured WT and p75−/− animals, p55−/− mice demonstrated a twofold reduction in IH. Additionally, p55−/− mice demonstrated a decrease in expression of nuclear factor-κB mRNA and protein. These observations suggest an important role for the p55 receptor in IH after mechanical endoluminal injury. Suppression of the transcriptional activator nuclear factor-κB may provide a mechanism by which p55-mediated IH is attenuated.
Glycogen phosphorylase and pyruvate dehydrogenase transformation in white muscle of trout during high-intensity exercise
Authors: Richards Jeff G. , Heigenhauser George J. F. , Wood Chris M.
Published: March 2015

We examined the regulation of glycogen phosphorylase (Phos) and pyruvate dehydrogenase (PDH) in white muscle of rainbow trout during a continuous bout of high-intensity exercise that led to exhaustion in 52 s. The first 10 s of exercise were supported by creatine phosphate hydrolysis and glycolytic flux from an elevated glycogenolytic flux and yielded a total ATP turnover of 3.7 μmol · g wet tissue−1· s−1. The high glycolytic flux was achieved by a large transformation of Phos into its active form. Exercise performed from 10 s to exhaustion was at a lower ATP turnover rate (0.5 to 1.2 μmol · g wet tissue−1· s−1) and therefore at a lower power output. The lower ATP turnover was supported primarily by glycolysis and was reduced because of posttransformational inhibition of Phos by glucose 6-phosphate accumulation. During exercise, there was a gradual activation of PDH, which was fully transformed into its active form by 30 s of exercise. Oxidative phosphorylation, from PDH activation, only contributed 2% to the total ATP turnover, and there was no significant activation of lipid oxidation. The time course of PDH activation was closely associated with an increase in estimated mitochondrial redox (NAD+-to-NADH concentration ratio), suggesting that O2was not limiting during high-intensity exercise. Thus anaerobiosis may not be responsible for lactate production in trout white muscle during high-intensity exercise.
Functional restitution of cardiac control in heart transplant patients
Authors: Toledo Eran , Pinhas Itzhak , Aravot Dan , Almog Yael , Akselrod Solange
Published: March 2015

Cardiovascular control is fundamentally altered after heart transplantation (HT) because of surgical denervation of the heart. The main goal of this work was the noninvasive characterization of cardiac rate control mechanisms after HT and the understanding of their nature. We obtained 25 recordings from 13 male HT patients [age = 28–68 yr, time after transplant (TAT) = 0.5–62.5 mo]. The control group included 14 healthy men (age = 28–59 yr). Electrocardiogram, continuous blood pressure (BP), and respiration were recorded for 45 min in the supine position and then during active change of posture (CP) to standing. The signals were analyzed in the time domain [mean and variance of heart rate (HR) and rise time of HR in response to CP] and the frequency domain [low and high frequency (LF and HF)]. Our principal finding was the consistent pattern of evolution of the HR response to standing: from no response, via a slow response (>40 s, TAT > 6 wk), to a fast increase (<20 s, TAT > 24 mo). HR response correlated with TAT ( P < 0.001). LF correlated with HR response to CP ( P < 0.0001); HF and HR did not. An important finding was the presence of very-high-frequency peaks in the power spectrum of HR and BP fluctuations. Extensive arrhythmias tended to appear at the TAT that corresponds to the transition from slow to fast HR response to CP. Our results indicate a biphasic evolution in cardiac control mechanisms from lack of control to a first-order control loop followed by partial sympathetic reinnervation and, finally, the direct effect of the old sinoatrial node on the pacemaker cell of the new sinoatrial node. There was no indication of vagal reinnervation.
Glucagon-like peptide 1-(7–36) amide acts at lateral and medial hypothalamic sites to suppress feeding in rats
Authors: Schick Rafael R. , Zimmermann Jens P. , Walde Thomas vorm , Schusdziarra Volker
Published: March 2015

Glucagon-like peptide 1-(7–36) amide (GLP-1) potently inhibits rat feeding behavior after central administration. Because third ventricular injection of GLP-1 appeared to be less effective than lateral ventricular injection, we have reexamined this issue. In addition, we attempted to identify brain regions other than the paraventricular nucleus of the hypothalamus that are sensitive toward GLP-1-induced feeding suppression. Finally, we examined the local role of endogenous GLP-1 by specific GLP-1 receptor blockade. After lateral ventricular injection, GLP-1 significantly inhibited food intake of 24-h-fasted rats in a dose-dependent fashion with a minimal effective dose of 1 μg. After third ventricular injection, GLP-1 (1 μg) was similarly effective in suppressing food intake, which extends previous findings. Intracerebral microinjections of GLP-1 significantly suppressed food intake in the lateral (LH), dorsomedial (DMH), and ventromedial hypothalamus (VMH), but not in the medial nucleus of the amygdala. The minimal effective dose of GLP-1 was 0.3 μg at LH sites and 1 μg at DMH or VMH sites. LH microinjections of exendin-(9–39) amide, a GLP-1 receptor antagonist, at 1 or 2.5 μg did not alter feeding behavior in 24-h-fasted rats. In satiated animals, however, a single LH injection of 1 μg exendin-(9–39) amide significantly augmented food intake, but only during the first 20 min (0.6 vs. 0.1 g). With three repeated injections of 2.5 μg exendin-(9–39) amide every 20 min, 1-h food intake was significantly increased by 300%. These data strongly support and extend the concept of GLP-1 as a physiological regulator of food intake in the hypothalamus.
Mechanisms of salt-sensitive hypertension: role of renal medullary inducible nitric oxide synthase
Authors: Tian Niu , Gannon Anthony W. , Khalil Raouf A. , Manning R. Davis
Published: March 2015

The goal of this study was to determine the role of renal medullary inducible nitric oxide synthase (iNOS) in the arterial pressure, renal hemodynamic, and renal excretory changes that occur in Dahl/Rapp salt-resistant (R) and salt-sensitive (S) rats during high Na intake. Forty R and S rats, equipped with indwelling arterial, venous, and renal medullary catheters, were subjected to high (8%) Na intake, and selective iNOS inhibition was achieved with continuous intravenous or renal medullary interstitial infusion of aminoguanidine (AG; 3.075 mg · kg−1· h−1). After 5 days of AG, mean arterial pressure increased to 132 ± 2% control in the S rats with high Na intake and intramedullary AG compared with 121 ± 4% control ( P < 0.05) in the S rats with high Na intake alone and 121 ± 2% control ( P < 0.05) in the S rats with high Na intake and intravenous AG. AG did not change arterial pressure in R rats. AG also caused little change in renal hemodynamics, urinary Na, or H2O excretion or ACh-induced aortic vasorelaxation in R or S rats. The data suggest that during high Na intake, nitric oxide produced by renal medullary iNOS helps to prevent excessive increases in arterial pressure in the Dahl S rat but not the R rat.