bluuebunny/crossref_metadata_2025 huggingface dataset:
Temperature-dependent expression of sarcolemmal K+currents in rainbow trout atrial and ventricular myocytes
Authors: Vornanen Matti , Ryökkynen Ari , Nurmi Antti
Published: March 2015

Temperature has a strong influence on the excitability and the contractility of the ectothermic heart that can be alleviated in some species by temperature acclimation. The molecular mechanisms involved in the temperature-induced improvement of cardiac contractility and excitability are, however, still poorly known. The present study examines the role of sarcolemmal K+currents from rainbow trout ( Oncorhynchus mykiss) cardiac myocytes after thermal acclimation. The two major K+conductances of the rainbow trout cardiac myocytes were identified as the Ba2+-sensitive background inward rectifier current ( IK1) and the E-4031-sensitive delayed rectifier current ( IKr). In atrial cells, the density of IK1is very low and the density of IKris remarkably high. The opposite is true for ventricular cells. Acclimation to cold (4°C) modified the two K+currents in opposite ways. Acclimation to cold increases the density of IKrand depresses the density of IK1. These changes in repolarizing K+currents alter the shape of the action potential, which is much shorter in cold-acclimated than warm-acclimated (17°C) trout. These results provide the first concrete evidence that K+channels of trout cardiac myocytes are adaptable units that provide means to regulate cardiac excitability and contractility as a function of temperature.
Erectile dysfunction in spontaneously hypertensive rats: pathophysiological mechanisms
Authors: Behr-Roussel Delphine , Chamiot-Clerc Philippe , Bernabe Jacques , Mevel Katell , Alexandre Laurent , Safar Michel E. , Giuliano François
Published: March 2015

Hypertensive men have a higher prevalence of erectile dysfunction (ED) than the general population. Experimental evidence of ED in hypertensive animals is scarce. This study evaluates the erectile function of spontaneously hypertensive rats (SHR) and age-matched normotensive Wistar-Kyoto rats (WKY) in vivo by the increase in intracavernosal pressure after electrical stimulation of the cavernous nerve (CN) and by isometric tension studies on corporal strips. Frequency-dependent erectile responses to CN stimulations were reduced in SHR. Phenylephrine induced lower corporal contractions in SHR although pD2values were similar to WKY. Endothelium-dependent relaxations to ACh were impaired significantly in SHR, and indomethacin improved these relaxations in both WKY and SHR, the latter thus reaching values similar to WKY. Corporal relaxations to sodium nitroprusside were enhanced in SHR. Thus a dysfunctional α-adrenergic contraction of the corporal smooth muscle, an increased cyclooxygenase-dependent constrictor tone, and/or a defect in endothelium-dependent reactivity are associated with the altered erectile mechanisms in SHR. Drugs targeting endothelial dysfunction may delay the occurrence of ED as a complication of hypertension.
Exercise elicits phase shifts and acute alterations of melatonin that vary with circadian phase
Authors: Buxton Orfeu M. , Lee Calvin W. , L'Hermite-Balériaux Mireille , Turek Fred W. , Van Cauter Eve
Published: March 2015

To examine the immediate phase-shifting effects of high-intensity exercise of a practical duration (1 h) on human circadian phase, five groups of healthy men 20–30 yr of age participated in studies involving no exercise or exposure to morning, afternoon, evening, or nocturnal exercise. Except during scheduled sleep/dark and exercise periods, subjects remained under modified constant routine conditions allowing a sleep period and including constant posture, knowledge of clock time, and exposure to dim light intensities averaging (±SD) 42 ± 19 lx. The nocturnal onset of plasma melatonin secretion was used as a marker of circadian phase. A phase response curve was used to summarize the phase-shifting effects of exercise as a function of the timing of exercise. A significant effect of time of day on circadian phase shifts was observed ( P < 0.004). Over the interval from the melatonin onset before exercise to the first onset after exercise, circadian phase was significantly advanced in the evening exercise group by 30 ± 15 min (SE) compared with the phase delays observed in the no-exercise group (−25 ± 14 min, P < 0.05). Phase shifts in response to evening exercise exposure were attenuated on the second day after exercise exposure and no longer significantly different from phase shifts observed in the absence of exercise. Unanticipated transient elevations of melatonin levels were observed in response to nocturnal exercise and in some evening exercise subjects. Taken together with the results from previous studies in humans and diurnal rodents, the current results suggest that 1) a longer duration of exercise exposure and/or repeated daily exposure to exercise may be necessary for reliable phase-shifting of the human circadian system and that 2) early evening exercise of high intensity may induce phase advances relevant for nonphotic entrainment of the human circadian system.
Aging and assessment of physiological strain during exercise-heat stress
Authors: Moran Daniel S. , Kenney W. Larry , Pierzga Jane M. , Pandolf Kent B.
Published: March 2015

The purpose of this study was to evaluate the physiological strain index (PSI) for different age groups during exercise-heat stress (EHS). PSI was applied to three different databases. First, from young and middle-age men (21 ± 2 and 46 ± 5 yr, respectively) matched ( n = 9 each, P > 0.05) for maximal aerobic power. Subjects were heat acclimated by daily treadmill walking for two 50-min bouts separated by 10-min rest for 10 days in a hot-dry environment [49°C, 20% relative humidity (RH)]. The second database involved a group ( n = 8) of young (YA) and a group ( n = 7) of older (OA) men (26 ± 1 and 69 ± 1 yr, respectively) who underwent 16 wk of aerobic training and two control groups ( n = 7 each) who were matched for age to YA and OA. These four groups performed EHS at 36°C, 40% RH on a cycle ergometer for 60 min at 60% maximal aerobic power before and after training. The third database was obtained from three groups of postmenopausal women and a group of 10 men. Two groups of women ( n = 8 each) were undergoing hormone replacement therapy, estrogen or estrogen plus progesterone, and the third group ( n = 9) received no hormone replacement. Subjects were over 50 yr and performed the same EHS: exercising at 36°C, 40% RH on a cycle ergometer for 60 min. PSI assessed the strain for all three databases and reported differences were significant at P < 0.05. This index rated the strain in rank order, whereas the postacclimation and posttraining groups were assessed as having less strain than the preacclimation and pretraining groups. Furthermore, middle-aged women on estrogen replacement therapy had less strain than estrogen + progesterone and no hormone therapy. PSI evaluation was extended for men and women of different ages (50–70 yr) during acute EHS, heat acclimation, after aerobic training, and inclusive of women undergoing hormone replacement therapy.
Myocardial function in rat genetic models of low and high aerobic running capacity
Authors: Barbato John C. , Lee Soon Jin , Koch Lauren Gerard , Cicila George T.
Published: March 2015

We recently evaluated treadmill aerobic running capacity in 11 inbred strains of rats and found that isolated working left ventricular function correlated ( r = 0.86) with aerobic running capacity. Among these 11 strains the Buffalo (BUF) hearts produced the lowest and the DA hearts the highest isolated cardiac output. The goal of this study was to investigate the components of cardiac function (i.e., coronary flow, heart rates, stroke volume, contractile dynamics, and cross-bridge cycling) to characterize further the BUF and DA inbred strains as potential models of contrasting myocardial performance. Cardiac performance was assessed using the Langendorff-Neely working heart preparation. Isolated DA hearts were superior ( P< 0.05) to the BUF hearts for cardiac output (63%), stroke volume (60%), aortic +dP/d t (47%), and aortic −dP/d t(46%). The mean α/β-myosin heavy chain (MHC) isoform ratio for DA hearts was 21-fold higher relative to BUF hearts. At the steady-state mRNA level, DA hearts had a fivefold higher α/β-ratio than the BUF hearts. The mean rate of ATP hydrolysis by MHCs was 64% greater in DA compared with BUF ventricles. These data demonstrate that the BUF and DA strains can serve as genetic models of contrasting low and high cardiac function.
Directionality of coupling of physiological subsystems: age-related changes of cardiorespiratory interaction during different sleep stages in babies
Authors: Mrowka Ralf , Cimponeriu Laura , Patzak Andreas , Rosenblum Michael G.
Published: March 2015

Activity of many physiological subsystems has a well-expressed rhythmic character. Often, a dependency between physiological rhythms is established due to interaction between the corresponding subsystems. Traditional methods of data analysis allow one to quantify the strength of interaction but not the causal interrelation that is indispensable for understanding the mechanisms of interaction. Here we present a recently developed method for quantification of coupling direction and apply it to an important problem. Namely, we study the mutual influence of respiratory and cardiovascular rhythms in healthy newborns within the first 6 mo of life in quiet and active sleep. We find an age-related change of the coupling direction: the interaction is nearly symmetric during the first days and becomes practically unidirectional (from respiration to heart rhythm) at the age of 6 mo. Next, we show that the direction of interaction is mainly determined by respiratory frequency. If the latter is less than ≈0.6 Hz, the interaction occurs dominantly from respiration to heart. With higher respiratory frequencies that only occur at very young ages, the dominating direction is less pronounced or even abolished. The observed dependencies are not related to sleep stage, suggesting that the coupling direction is determined by system-inherent dynamical processes, rather than by functional modulations. The directional analysis may be applied to other interacting narrow band oscillatory systems, e.g., in the central nervous system. Thus it is an important step forward in revealing and understanding causal mechanisms of interactions.
Activation of adenylyl cyclases, regulation of insulin status, and cell survival by Gαolf in pancreatic β-cells
Authors: Régnauld Karine L. , Leteurtre Emmanuelle , Gutkind Silvio J. , Gespach Christian P. , Emami Shahin
Published: March 2015

Because we recently identified the Gαolf subunit in rat pancreatic β-cells, we investigated the downstream effectors and the biological functions of this G protein in HEK-293T cells and the insulin-secreting mouse βTC-3 cell line. With the use of transient transfection of HEK-293T cells with constitutively activated Gαolf (GαolfQ214L, i.e., AGαolf), together with expression vectors encoding the adenylyl cyclase (AC) isoforms (AC-I to -VIII and soluble AC), compared with cotransfections using AGαs (GαsR201C), we observed that AGαolf preferentially activates AC-I and -VIII, which are also expressed in β-cells. Stable overexpression of wild-type or AGαolf in βTC-3 cells resulted in partial attenuation of insulin secretion and biosynthesis, suggesting that chronic activation of the Gαolf-signaling pathway is associated with β-cell desensitization. In agreement, transfected βTC-3 cells present a decreased insulin content with respect to parental cells, whereas the proinsulin convertases PC-1 and PC-2 were unaffected. Furthermore, βTC-3-AGαolf cells are resistant to serum starvation-induced apoptosis. Our findings suggest that Gαolf is involved in insulin status, cell survival, and regeneration of the insulin-secreting β-cells during development and diabetes.
Antipyretic role of the NO-cGMP pathway in the anteroventral preoptic region of the rat brain
Authors: Steiner Alexandre A. , Antunes-Rodrigues Jose , McCann Samuel M. , Branco Luiz G. S.
Published: March 2015

We tested the hypothesis that nitric oxide (NO) acts in the anteroventral preoptic region (AVPO) modulating fever. To this end, body core temperature (Tc) of rats was monitored by biotelemetry before and after pharmacological modulation of the NO pathway. Nitrite/nitrate and cGMP in the anteroventral third ventricular region (AV3V), where the AVPO is located, were also determined. Intra-AVPO microinjection of the NO synthase (NOS) inhibitor N G-monomethyl-l-arginine (l-NMMA, 12.5 μg) did not affect basal Tc, but it enhanced the early stage of lipopolysaccharide (LPS) fever, indicating that NO plays an antipyretic role in the AVPO. In agreement, intra-AVPO microinjection of the NO donor sodium nitroprusside (5 μg) reduced Tc. The antipyretic effect of NO seems to be mediated by cGMP because 1) NO has been shown to activate soluble guanylate cyclase, 2) intra-AVPO microinjection of 8-bromo-cGMP (8-BrcGMP) reduced Tc, and 3) the changes in AV3V levels of nitrite/nitrate and cGMP were similar in the course of fever. Additionally, we observed that nitrite/nitrate and cGMP levels decreased in the AV3V after, but not before, the onset of LPS fever, showing that the activity of the NO-cGMP pathway is reduced in the AV3V after intraperitoneal LPS, a mechanism that could contribute to the genesis and maintenance of fever. It was also observed that the efficacy of 8-BrcGMP in reducing Tc in the AVPO is increased after LPS, emphasizing that the NO-cGMP pathway is antipyretic. This response could explain why intra-AVPOl-NMMA enhanced the early stage of LPS fever, even though the activity of the NO pathway before the onset of fever was unchanged. In summary, these data support an antipyretic role of the NO-cGMP pathway in the AVPO.
Effect of interleukin-18 on mouse core body temperature
Authors: Gatti Silvia , Beck Jennifer , Fantuzzi Giamila , Bartfai Tamas , Dinarello Charles A.
Published: March 2015

We have studied, using a telemetry system, the pyrogenic properties of recombinant murine interleukin-18 (rmIL-18) injected into the peritoneum of C57BL/6 mice. The effect of IL-18 was compared with the febrile response induced by human IL-1β, lipopolysaccharide (LPS), and recombinant murine interferon-γ (rmIFN-γ). Both IL-1β and LPS induced a febrile response within the first hour after the intraperitoneal injection, whereas rmIL-18 (10–200 μg/kg) and rmIFN-γ (10–150 μg/kg) did not cause significant changes in the core body temperature of mice. Surprisingly, increasing doses of IL-18, injected intraperitoneally 30 min before IL-1β, significantly reduced the IL-1β-induced fever response. In contrast, the same pretreatment with IL-18 did not modify the febrile response induced by LPS. IFN-γ does not seem to play a role in the IL-18-mediated attenuation of IL-1β-induced fever. In fact, there was no elevation of IFN-γ in the serum of mice treated with IL-18, and a pretreatment with IFN-γ did not modify the fever response induced by IL-1β. We conclude that IL-18 is not pyrogenic when injected intraperitoneally in C57BL/6 mice. Furthermore, a pretreatment with IL-18, 30 min before IL-1β, attenuates the febrile response induced by IL-1β.
Influence of respiratory network drive on phrenic motor output evoked by activation of cat pre-Bötzinger complex
Authors: Solomon Irene C.
Published: March 2015

10.1152/ajpregu.00395.2002. We have previously demonstrated that microinjection of dl-homocysteic acid (DLH), a glutamate analog, into the pre-Bötzinger complex (pre-BötC) can produce either phasic or tonic excitation of phrenic nerve discharge during hyperoxic normocapnia. Breathing, however, is influenced by input from both central and peripheral chemoreceptor activation. This influence of increased respiratory network drive on pre-BötC-induced modulation of phrenic motor output is unclear. Therefore, these experiments were designed to examine the effects of chemical stimulation of neurons (DLH; 10 mM; 10–20 nl) in the pre-BötC during hyperoxic modulation of CO2 (i.e., hypercapnia and hypocapnia) and during normocapnic hypoxia in chloralose-anesthetized, vagotomized, mechanically ventilated cats. For these experiments, sites were selected in which unilateral microinjection of DLH into the pre-BötC during baseline conditions of hyperoxic normocapnia [arterial Pco 2 (PaCO2 ) = 37–43 mmHg; n = 22] produced a tonic (nonphasic) excitation of phrenic nerve discharge. During hypercapnia (PaCO2 = 59.7 ± 2.8 mmHg; n= 17), similar microinjection produced excitation in which phasic respiratory bursts were superimposed on varying levels of tonic discharge. These DLH-induced phasic respiratory bursts had an increased frequency compared with the preinjection baseline frequency ( P < 0.01). In contrast, during hypocapnia (PaCO2 = 29.4 ± 1.5 mmHg; n= 11), microinjection of DLH produced nonphasic tonic excitation of phrenic nerve discharge that was less robust than the initial (normocapnic) response (i.e., decreased amplitude). During normocapnic hypoxia (PaCO2 = 38.5 ± 3.7; arterial Po 2 = 38.4 ± 4.4; n= 8) microinjection of DLH produced phrenic excitation similar to that seen during hypercapnia (i.e., increased frequency of phasic respiratory bursts superimposed on tonic discharge). These findings demonstrate that phrenic motor activity evoked by chemical stimulation of the pre-BötC is influenced by and integrates with modulation of respiratory network drive mediated by input from central and peripheral chemoreceptors.
Cardiovascular and renal control in NOS-deficient mouse models
Authors: Ortiz Pablo A. , Garvin Jeffrey L.
Published: March 2015

Nitric oxide (NO) plays an essential role in the maintenance of cardiovascular and renal homeostasis. Endogenous NO is produced by three different NO synthase (NOS) isoforms: endothelial NOS (eNOS), inducible NOS (iNOS), and neuronal NOS (nNOS). To investigate which NOS is responsible for NO production in different tissues, NOS knockout (−/−) mice have been generated for the three isoforms. This review focuses on the regulation of cardiovascular and renal function in relation to blood pressure homeostasis in the different NOS−/− mice. Although regulation of vascular tone and cardiac function in eNOS−/− has been extensively studied, far less is known about renal function in these mice. eNOS−/− mice are hypertensive, but the mechanism responsible for their high blood pressure is still not clear. Less is known about cardiovascular and renal control in nNOS−/− mice, probably because their blood pressure is normal. Recent data suggest that nNOS plays important roles in cardiac function, renal homeostasis, and regulation of vascular tone under certain conditions, but these are only now beginning to be studied. Inasmuch as iNOS is absent from the cardiovascular system under physiological conditions, it may become important to blood pressure regulation only during pathological conditions related to inflammatory processes. However, iNOS is constitutively expressed in the kidney, where its function is largely unknown. Overall, the study of NOS knockout mice has been very useful and produced many answers, but it has also raised new questions. The appearance of compensatory mechanisms suggests the importance of the different isoforms to specific processes, but it also complicates interpretation of the data. In addition, deletion of a single gene may have physiologically significant effects in addition to those being studied. Thus the presence or absence of a specific phenotype may not reflect the most important physiological function of the absent gene.
Is the chronically denervated kidney supersensitive to catecholamines?
Authors: Ramchandra Rohit , Barrett Carolyn J. , Guild Sarah-Jane , Malpas Simon C.
Published: March 2015

One method for discerning the role of the renal sympathetic nerves in the regulation of renal function has been to chronically denervate one kidney. One concern with this approach is that increased renal responsiveness to plasma levels of norepinephrine may develop over time. This may reduce the apparent magnitude of the effect of the renal nerves or indeed completely mask their effect. In the present experiment, we used the rabbit unilateral denervated kidney model to examine the acute renal blood flow responses to phenylephrine to determine if there were differences between the responses in chronically denervated kidneys compared with either intact or acutely denervated kidneys. In addition, we examined the responses in rabbits that had been made hypertensive using a continuous infusion of ANG II for 7 wk. We found that chronic denervation did not result in increased renal responsiveness to phenylephrine compared with either the intact or acutely denervated kidney, suggesting that differences in renal function between renal nerve-intact and -denervated kidneys observed in previous studies are unlikely to be confounded by supersensitivity. These results suggest that the unilateral denervated kidney model is a valid model to study the role of the renal nerves in the regulation of renal function.
Triggering of sarcoplasmic reticulum Ca2+release and contraction by reverse mode Na+/Ca2+exchange in trout atrial myocytes
Authors: Hove-Madsen Leif , Llach Anna , Tibbits Glen F. , Tort Lluis
Published: March 2015

Whole cell patch clamp and intracellular Ca2+transients in trout atrial cardiomyocytes were used to quantify calcium release from the sarcoplasmic reticulum (SR) and examine its dependency on the Ca2+trigger source. Short depolarization pulses (2–20 ms) elicited large caffeine-sensitive tail currents. The Ca2+carried by the caffeine-sensitive tail current after a 2-ms depolarization was 0.56 amol Ca2+/pF, giving an SR Ca2+release rate of 279 amol Ca2+· pF−1· s−1or 4.3 mM/s. Depolarizing cells for 10 ms to different membrane potentials resulted in a local maximum of SR Ca2+release, intracellular Ca2+transient, and cell shortening at 10 mV. Although 100 μM CdCl2abolished this local maximum, it had no effect on SR Ca2+release elicited by a depolarization to 110 or 150 mV, and the SR Ca2+release was proportional to the membrane potential in the range −50 to 150 mV with 100 μM CdCl2. Increasing the intracellular Na+concentration ([Na+]) from 10 to 16 mM enhanced SR Ca2+release but reduced cell shortening at all membrane potentials examined. In the absence of TTX, SR Ca2+release was potentiated with 16 mM but not 10 mM pipette [Na+]. Comparison of the total sarcolemmal Ca2+entry and the Ca2+released from the SR gave a gain factor of 18.6 ± 7.7. Nifedipine (Nif) at 10 μM inhibited L-type Ca2+current ( ICa) and reduced the time integral of the tail current by 61%. The gain of the Nif-sensitive SR Ca2+release was 16.0 ± 4.7. A 2-ms depolarization still elicited a contraction in the presence of Nif that was abolished by addition of 10 mM NiCl2. The gain of the Nif-insensitive but NiCl2-sensitive SR Ca2+release was 14.8 ± 7.1. Thus both reverse-mode Na+/Ca2+exchange (NCX) and ICacan elicit Ca2+release from the SR, but ICais more efficient than reverse-mode NCX in activating contraction. This difference may be due to extrusion of a larger fraction of the Ca2+released from the SR by reverse-mode NCX rather than a smaller gain for NCX-induced Ca2+release.
Myogenic responses and compliance of mesenteric and splenic vasculature in the rat
Authors: Brookes Zoë L. S. , Kaufman Susan
Published: March 2015

In the rat, the spleen is a major site of fluid efflux out of the blood. By contrast, the mesenteric vasculature serves as a blood reservoir. We proposed that the compliance and myogenic responses of these vascular beds would reflect their different functional demands. Mesenteric and splenic arterioles (∼150–200 μm) and venules (<250 μm) from rats anesthetized with pentobarbital sodium were mounted in a pressurized myograph. Mesenteric arterial diameter decreased from 146 ± 6 to 133 ± 6 μm on raising intraluminal pressures from 80 to 120 mmHg. This response was enhanced in the presence of Nω-nitro-l-arginine methyl ester (l-NAME; 139 ± 6 to 112 ± 7 μm). There was no such myogenic response in the splenic arterioles, except in the presence of l-NAME (194 ± 4 to 164 ± 4.2 μm). We propose that, whereas mesenteric arterioles exhibit myogenic responses, this is normally masked by NO-mediated dilation in the splenic vessels. The mesenteric venules were highly distensible (active, 184 ± 15 to 320 ± 30.9 μm; passive in Ca2+-free media, 209 ± 31 to 344 ± 27 μm; 4–8 mmHg) compared with the splenic vessels (active, 169 ± 11 to 184 ± 16 μm; passive, 187 ± 12 to 207 ± 17 μm). We conclude that, in response to an increase in perfusion pressure, mesenteric arterial diameter would decrease to limit the changes in flow and microvascular pressure. In addition, mesenteric venous capacitance would increase. By contrast, splenic arterial diameter would increase, while there would be little change in venous diameter. This would enhance the increase in intrasplenic microvascular pressure and increase fluid extravasation.
Unloading arterial baroreceptors causes neurogenic hypertension
Authors: Thrasher Terry N.
Published: March 2015

We developed a new model to examine the role of arterial baroreceptors in the long-term control of mean arterial pressure (MAP) in dogs. Baroreceptors in the aortic arch and one carotid sinus were denervated, and catheters were implanted in the descending aorta and common carotid arteries. MAP and carotid sinus pressure (CSP) averaged 104 ± 2 and 102 ± 2 mmHg (means ± 1 SE), respectively, during a 5-day control period. Baroreceptor unloading was induced by ligation of the common carotid artery proximal to the innervated sinus ( n = 6 dogs). MAP and CSP averaged 127 ± 7 and 100 ± 3 mmHg, respectively, during the 7-day period of baroreceptor unloading. MAP was significantly elevated ( P < 0.01) compared to control, but CSP was unchanged. Heart rate and plasma renin activity increased significantly in response to baroreceptor unloading. Removal of the ligature to restore normal flow through the carotid resulted in normalization of all variables. Ligation of the carotid below a denervated sinus ( n = 4) caused a significant decrease in CSP but no systemic hypertension. These results indicate that chronic unloading of carotid baroreceptors can produce neurogenic hypertension and provide strong evidence that arterial baroreceptors are involved in the long-term control of blood pressure.
Manipulation of plasma uric acid in broiler chicks and its effect on leukocyte oxidative activity
Authors: Simoyi Melvin F. , Van Dyke Knox , Klandorf Hillar
Published: March 2015

Birds have high metabolic rates, body temperatures, and plasma glucose concentrations yet physiologically age at a rate slower than comparably sized mammals. These studies were designed to test the hypothesis that the antioxidant uric acid protects birds against oxidative stress. Mixed sex broiler chicks (3 wk old) were fed diets supplemented or not with purines (0.6 mol hypoxanthine or inosine). Study 1 consisted of 18 female Cobb × Cobb broilers that were fed purines for 7 days, whereas study 2 consisted of 12 males in a 21-day trial. Study 3involved 30 mixed sex broilers that were fed 40 or 50 mg allopurinol/kg body mass (BM) for 21 days, a drug that lowers plasma uric acid (PUA). PUA and leukocyte oxidative activity (LOA) were determined weekly for all studies. For study 2, pectoralis major shear force, relative kidney and liver sizes (RKS and RLS), and plasma glucose concentrations were also determined. In study 1, PUA concentration was increased three- and twofold ( P < 0.001) in birds fed inosine or hypoxanthine, respectively, compared with control birds. LOA of birds supplemented with inosine was lower ( P < 0.05) than that of control or hypoxanthine birds. In study 2, PUA concentrations were increased fivefold ( P < 0.001) in birds fed inosine and twofold ( P < 0.001) in birds fed hypoxanthine compared with control birds at day 21. RKS (g/kg BM) was greater ( P < 0.001) for chicks fed purine diets compared with control chicks. Muscle shear value was lower ( P < 0.05) in chicks fed purine diets. PUA concentration was decreased ( P < 0.001) in birds consuming allopurinol diets, whereas LOA was increased ( P < 0.01) in study 3. These studies show that PUA concentrations can be related to oxidative stress in birds, which can be linked to tissue aging.
Dynamic modulation of cerebrovascular resistance as an index of autoregulation under tilt and controlled Pet CO2
Authors: Edwards Michael R. , Shoemaker J. Kevin , Hughson Richard L.
Published: March 2015

Transfer function analysis of the arterial blood pressure (BP)-mean flow velocity (MFV) relationship describes an aspect of cerebrovascular autoregulation. We hypothesized that the transfer function relating BP to cerebrovascular resistance (CVRi) would be sensitive to low-frequency changes in autoregulation induced by head-up tilt (HUT) and altered arterial Pco 2. Nine subjects were studied in supine and HUT positions with end-tidal Pco 2(Pet CO2 ) kept constant at normal levels: +5 and −5 mmHg. The BP-MFV relationship had low coherence at low frequencies, and there were significant effects of HUT on gain only at high frequencies and of Pco 2 on phase only at low frequencies. BP → CVRi had coherence >0.5 from very low to low frequencies. There was a significant reduction of gain with increased Pco 2 in the very low and low frequencies and with HUT at the low frequency. Phase was affected by Pco 2 in the very low frequencies. Transfer function analysis of BP → CVRi provides direct evidence of altered cerebrovascular autoregulation under HUT and higher levels of Pco 2.
Apoptosis in skeletal muscle with aging
Authors: Dirks Amie , Leeuwenburgh Christiaan
Published: March 2015

Sarcopenia may be partly due to a loss in total fiber number by apoptosis. We have investigated age-related alterations in the mitochondria-mediated pathway leading to apoptosis in the gastrocnemius muscle from 6-mo-old and 24-mo-old male Fisher 344 rats. Apoptosis (mono- and oligonucleosome fragmentation) in the gastrocnemius muscle was increased by 50% in the old rats compared with the adult animals. Furthermore, there was a significant correlation between cytosolic cytochrome c and caspase-3 activity, although neither cytochrome c nor caspase-3 activity increased significantly with age. Furthermore, there was a significant correlation between caspase-3 activity and mono- and oligonucleosome fragmentation in the old rats only. Mitochondrial Bcl-2 and Bax were not altered with age. In vitro experiments demonstrated that activation of the caspase cascade in skeletal muscle might be limited by procaspase-9 activation. This is the first study to explore the role of apoptosis in sarcopenia and suggests that subtle changes in apoptosis are involved.
Androgen-mediated induction of the kidney arachidonate hydroxylases is associated with the development of hypertension
Authors: Nakagawa Kiyoshi , Marji Jackleen S. , Schwartzman Michal L. , Waterman Michael R. , Capdevila Jorge H.
Published: March 2015

Hypertension is a leading cause of cardiovascular, cerebral, and renal disease morbidity and mortality, and epidemiological evidence suggests a role for sex-dependent mechanisms in the pathophysiology of hypertension. We show here that treatment of rats with 5α-dihydrotestosterone increases the activity of the kidney arachidonate ω/ω-1 hydroxylase and the biosynthesis of 20-HETE (165 and 177% of control untreated male and female rats, respectively) and raises the systolic blood pressures of male and females rats by 46 and 57 mmHg, respectively. These androgen effects are associated with an upregulation in the kidney levels of CYP 4A8 mRNA and a decrease in CYP 4A1 transcripts. Dissected renal microvessels, the target tissue for most of the prohypertensive actions of 20-HETE, show an androgen-dependent upregulation of vascular CYP 4A8 mRNA and a fourfold increase in 20-HETE synthase activity. We propose that androgens regulate renal function and systemic blood pressure through a combination of transcriptional and hemodynamic mechanisms that are ultimately responsible for the regulation of renovascular tone and function.
NTP pattern of avian embryonic red cells: role of RNA degradation and AMP deaminase/5′-nucleotidase activity
Authors: Baumann Rosemarie , Götz Robert , Dragon Stefanie
Published: March 2015

During terminal erythroid differentiation, degradation of RNA is a potential source for nucleotide triphosphates (NTPs) that act as allosteric effectors of hemoglobin. In this investigation, we assessed the developmental profile of RNA and purine/pyrimidine trinucleotides in circulating embryonic chick red blood cells (RBC). Extensive changes of the NTP pattern are observed which differ significantly from what is observed for adult RBC. The biochemical mechanisms have not been identified yet. Therefore, we studied the role of AMP deaminase and IMP/GMP 5′-nucleotidase, which are key enzymes for the regulation of the purine nucleotide pool. Finally, we tested the effect of major NTPs on the oxygen affinity of embryonic/adult hemoglobin. The results are as follows. 1) Together with ATP, UTP and CTP serve as allosteric effectors of hemoglobin. 2) Degradation of erythroid RNA is apparently a major source for NTPs. 3) Developmental changes of nucleotide content depend on the activities of key enzymes (AMP deaminase, IMP/GMP 5′-nucleotidase, and pyrimidine 5′-nucleotidase). 4) Oxygen-dependent hormonal regulation of AMP deaminase adjusts the red cell ATP concentration and therefore the hemoglobin oxygen affinity.
I. Time course of interventions and recovery sleep
Authors: Werth Esther , Cote Kimberly A. , Gallmann Eva , Borbély Alexander A. , Achermann Peter
Published: March 2015

Although repeated selective rapid eye movement (REM) sleep deprivation by awakenings during nighttime has shown that the number of sleep interruptions required to prevent REM sleep increases within and across consecutive nights, the underlying regulatory processes remained unspecified. To assess the role of circadian and homeostatic factors in REM sleep regulation, REM sleep was selectively deprived in healthy young adult males during a daytime sleep episode (7–15 h) after a night without sleep. Circadian REM sleep propensity is known to be high in the early morning. The number of interventions required to prevent REM sleep increased from the first to the third 2-h interval by a factor of two and then leveled off. Only a minor REM sleep rebound (11.6%) occurred in the following undisturbed recovery night. It is concluded that the limited rise of interventions during selective daytime REM sleep deprivation may be due to the declining circadian REM sleep propensity, which may partly offset the homeostatic drive and the sleep-dependent disinhibition of REM sleep.
Blood flows and nutrient uptakes in growth-restricted pregnancies induced by overnourishing adolescent sheep
Authors: Wallace Jacqueline M. , Bourke Deirdre A. , Aitken Raymond P. , Leitch Neil , Hay William W.
Published: March 2015

To establish physiological mechanisms for fetal growth restriction in pregnant adolescent ewes we studied uterine, fetal, and uteroplacental metabolism in ewes offered a high ( n = 12) or moderate ( n = 10) dietary intake. High intakes decreased placental (226 vs. 414 g, P < 0.001) and fetal weight (3,323 vs. 4,626 g, P < 0.01). Uterine blood flow was reduced absolutely (−36%) but proportional to conceptus weight; umbilical blood flow was reduced absolutely (−37%) and per fetal weight (−15%). Uterine oxygen uptake was decreased per conceptus weight (−14%); there was no change in fetal weight oxygen consumption. Uteroplacental oxygen consumption and clearance were reduced proportional to weight. Similar changes were measured for glucose fluxes and fetal glucose concentration; fetal insulin concentration was reduced. In this model of fetal growth restriction, therefore, maintenance of fetal weight-specific glucose and oxygen consumption rates are producing relative hypoglycemia and hypoxemia. This indicates that increased fetal glucose clearance and/or insulin sensitivity may be operating as compensatory mechanisms to preserve normal fetal metabolism while fetal growth is sacrificed.
II. Muscle atonia in non-REM sleep
Authors: Werth Esther , Achermann Peter , Borbély Alexander A.
Published: March 2015

One of the hallmarks of rapid eye movement (REM) sleep is muscle atonia. Here we report extended epochs of muscle atonia in non-REM sleep (MAN). Their extent and time course was studied in a protocol that included a baseline night, a daytime sleep episode with or without selective REM sleep deprivation, and a recovery night. The distribution of the latency to the first occurrence of MAN was bimodal with a first mode shortly after sleep onset and a second mode 40 min later. Within a non-REM sleep episode, MAN showed a U-shaped distribution with the highest values before and after REM sleep. Whereas MAN was at a constant level over consecutive 2-h intervals of nighttime sleep, MAN showed high initial values when sleep began in the morning. Selective daytime REM sleep deprivation caused an initial enhancement of MAN during recovery sleep. It is concluded that episodes of MAN may represent an REM sleep equivalent and that it may be a marker of homeostatic and circadian REM sleep regulating processes. MAN episodes may contribute to the compensation of an REM sleep deficit.
ATP stimulates the release of prostacyclin from perfused veins isolated from the hamster hindlimb
Authors: Hammer Leah W. , Overstreet Carmen R. , Choi Jaehwa , Hester Robert L.
Published: March 2015

ATP-stimulated prostacyclin release from veins was investigated using epigastric veins isolated from hamsters. Veins were perfused with MOPS-buffered physiological salt solution (PSS). ATP was administered into the perfusate, and the bath solution (MOPS-PSS) was collected and assayed for the presence of the stable prostacyclin metabolite 6-keto-PGF1α. ATP (100 μM) resulted in reproducible increases in bath concentration from 73 ± 22 to 279 ± 50 pg/ml ( P < 0.05, n = 5). This response was abolished by indomethacin (10 μM, P < 0.05). To ascertain whether the endothelium was the source of prostacyclin, endothelium was disrupted using air ( n = 10) or deoxycholic acid ( n = 6). Perfusion with air significantly reduced ( P < 0.05) but did not completely abolish ATP-stimulated release of prostacyclin, while deoxycholic acid totally abolished the response ( P < 0.05). The nonselective P2 receptor antagonist reactive blue 2 (100 μM) attenuated ATP-mediated release of prostacyclin but did not significantly alter ACh-stimulated release of prostacyclin. The nonselective adenosine receptor antagonist xanthine amine congener (1 μM) had no effect on ATP-stimulated release, and adenosine did not stimulate the release of prostacyclin. These results show that increases in intraluminal concentration of ATP stimulate abluminal release of prostacyclin from the venous endothelium. This effect is mediated by P2 receptors while adenosine and its receptors are not involved in this response.
Transepithelial sulfate transport by avian renal proximal tubule epithelium in primary culture
Authors: Dudas Paul L. , Renfro J. Larry
Published: March 2015

The mechanisms and control of transepithelial inorganic sulfate (Si) transport by primary cultures of chick renal proximal tubule monolayers in Ussing chambers were determined. The competitive anion, S2O32−(5 mM), reduced both unidirectional reabsorptive and secretory fluxes and net Sireabsorption with no effect on electrophysiological properties. The carbonic anhydrase (CA) inhibitor ethoxzolamide decreased net Sireabsorption ∼45%. CAII protein and activity were detected in isolated chick proximal tubules by immunoblots and biochemical assay, respectively. Cortisol reduced net Sireabsorption up to ∼50% in a concentration-dependent manner. Thyroid hormone increased net Sireabsorption threefold in 24 h, and parathyroid hormone (PTH) acutely stimulated net Sireabsorption ∼45%. These data indicate that CA participates in avian proximal tubule active transepithelial Sireabsorption, which cortisol directly inhibits and T3and PTH directly stimulate.
Effects of ANG II type 1 and 2 receptors on oxidative stress, renal NADPH oxidase, and SOD expression
Authors: Chabrashvili Tina , Kitiyakara Chagriya , Blau Jonathan , Karber Alex , Aslam Shakil , Welch William J. , Wilcox Christopher S.
Published: March 2015

Oxidative stress accompanies angiotensin (ANG) II infusion, but the role of ANG type 1 vs. type 2 receptors (AT1-R and AT2-R, respectively) is unknown. We infused ANG II subcutaneously in rats for 1 wk. Excretion of 8-isoprostaglandin F2α(8-Iso) and malonyldialdehyde (MDA) were related to renal cortical mRNA abundance for subunits of NADPH oxidase and superoxide dismutases (SODs) using real-time PCR. Subsets of ANG II-infused rats were given the AT1-R antagonist candesartan cilexetil (Cand) or the AT2-R antagonist PD-123,319 (PD). Compared to vehicle (Veh), ANG II increased 8-Iso excretion by 41% (Veh, 5.4 ± 0.8 vs. ANG II, 7.6 ± 0.5 pg/24 h; P < 0.05). This was prevented by Cand (5.6 ± 0.5 pg/24 h; P < 0.05) and increased by PD (15.8 ± 2.0 pg/24 h; P < 0.005). There were similar changes in MDA excretion. Compared to Veh, ANG II significantly ( P < 0.005) increased the renal cortical mRNA expression of p22phox(twofold), Nox-1 (2.6-fold), and Mn-SOD (1.5-fold) and decreased expression of Nox-4 (2.1-fold) and extracellular (EC)-SOD (2.1-fold). Cand prevented all of these changes except for the increase in Mn-SOD. PD accentuated changes in p22phoxand Nox-1 and increased p67phox. We conclude that ANG II infusion stimulates oxidative stress via AT1-R, which increases the renal cortical mRNA expression of p22phoxand Nox-1 and reduces abundance of Nox-4 and EC-SOD. This is offset by strong protective effects of AT2-R, which are accompanied by decreased expression of p22phox, Nox-1, and p67phox.
5-HT1Areceptor agonist 8-OH-DPAT acts in the hindbrain to reverse the sympatholytic response to severe hemorrhage
Authors: Scrogin Karie E.
Published: March 2015

Central administration of serotonergic 5-HT1Areceptor agonists delays the reflex sympatholytic response to severe hemorrhage in conscious rats. To determine the region where 5-HT1Areceptor agonists act to mediate this response, recovery of mean arterial pressure (MAP), heart rate (HR), and renal sympathetic nerve activity (RSNA) was compared in hemorrhaged rats after injection of the selective 5-HT1Aagonist, (+)-8-hydroxy-2-(di- n-propylamino)tetralin (8-OH-DPAT), in various regions of the cerebroventricular system or the systemic circulation. Three minutes after injection of 8-OH-DPAT (48 nmol/kg), MAP and RSNA were higher in hemorrhaged rats given drug in the fourth ventricle (94 ± 5 mmHg, 82 ± 18% of baseline) or the systemic circulation (90 ± 4 mmHg, 113 ± 15% of baseline) than in rats given drug in the Aqueduct of Sylvius (63 ± 4 mmHg, 27 ± 11% of baseline), the lateral ventricle (42 ± 3 mmHg, −8 ± 18% of baseline), or in rats given saline in various brain regions (47 ± 5 mmHg, −42 ± 10% of baseline). A lower-dose injection of 8-OH-DPAT (10 nmol/kg) also accelerated the recovery of MAP and RSNA in hemorrhaged rats when given in the fourth ventricle (94 ± 26 mmHg, 72 ± 33% of baseline 3 min after injection) but not the systemic circulation (46 ± 4 mmHg, −25 ± 30% of baseline). These data indicate that 8-OH-DPAT acts on receptors in the hindbrain to reverse the sympatholytic response to hemorrhage in conscious rats.
IL-1β stimulates IL-6 production in cultured skeletal muscle cells through activation of MAP kinase signaling pathway and NF-κB
Authors: Luo Guangjo , Hershko Dan D. , Robb Bruce W. , Wray Curtis J. , Hasselgren Per-Olof
Published: March 2015

Recent studies suggest that the skeletal muscle may be a significant site of IL-6 production in various conditions, including exercise, inflammation, hypoperfusion, denervation, and local muscle injury. The mediators and molecular mechanisms regulating muscle IL-6 production are poorly understood. We tested the hypothesis that IL-6 production in muscle cells is regulated by IL-1β and that mitogen-activated protein (MAP) kinase signaling and NF-κB activation are involved in IL-1β-induced IL-6 production. Cultured C2C12 cells, a mouse skeletal muscle cell line, were treated with different concentrations (0.1–2 ng/ml) of IL-1β in the absence or presence of the p38 MAP kinase inhibitor SB-208350 or the p42/44 inhibitor PD-98059. Protein and gene expression of IL-6 were determined by ELISA and real-time PCR, respectively. NF-κB DNA binding activity was determined by electrophoretic mobility shift assay and by transfecting myocytes with a luciferase reporter plasmid containing a promoter construct with multiple repeats of NF-κB binding site. Treatment of myotubes with IL-1β resulted in a dose- and time-dependent increase of IL-6 production accompanied by an ∼25-fold increase in IL-6 mRNA levels. IL-1β stimulated NF-κB DNA binding activity and gene activation. SB-208350 and PD-98059 inhibited the increase in IL-6 production induced by IL-1β. The present results support the concept that skeletal muscle is an important site of IL-6 production. In addition, the results suggest the IL-1β regulates muscle IL-6 production at least in part by activating the MAP kinase pathway and NF-κB.
Proteasome inhibitors induce heat shock response and increase IL-6 expression in human intestinal epithelial cells
Authors: Pritts Timothy A. , Hungness Eric S. , Hershko Dan D. , Robb Bruce W. , Sun Xiaoyan , Luo Guang-Ju , Fischer Josef E. , Wong Hector R. , Hasselgren Per-Olof
Published: March 2015

In previous studies, the heat shock response, induced by hyperthermia or sodium arsenite, increased interleukin (IL)-6 production in intestinal mucosa and cultured human enterocytes. A novel way to induce the heat shock response, documented in other cell types, is treatment with proteasome inhibitors. It is not known if proteasome inhibition induces heat shock in enterocytes or influences IL-6 production. Here we tested the hypothesis that treatment of cultured Caco-2 cells, a human intestinal epithelial cell line, with proteasome inhibitors induces the heat shock response and stimulates IL-6 production. Treatment of Caco-2 cells with one of the proteasome inhibitors MG-132 or lactacystin activated the transcription factor heat shock factors (HSF)-1 and -2 and upregulated cellular levels of the 72-kDa heat shock protein HSP-72. The same treatment resulted in increased gene and protein expression of IL-6, a response that was blocked by quercetin. Additional experiments revealed that the IL-6 gene promoter contains a HSF-responsive element and that the IL-6 gene may be regulated by the heat shock response. The present results suggest that proteasome inhibition induces heat shock response and IL-6 production in enterocytes and that IL-6 may be a heat shock-responsive gene, at least under certain circumstances. The observations are important considering the multiple biological roles of IL-6, both locally in the gut mucosa and systemically, and considering recent proposals in the literature to use proteasome inhibitors in the clinical setting to induce the heat shock response.