bluuebunny/crossref_metadata_2025 huggingface dataset:
Cardioprotective actions of endogenous IL-10 are independent of iNOS
Authors: Jones Steven P. , Trocha Steven D. , Lefer David J.
Published: December 2017

Myocardial ischemia-reperfusion (I/R) is a well-known stimulus for acute inflammatory responses that promote cell death and impair pump function. Interleukin-10 (IL-10) is an endogenous, potent anti-inflammatory cytokine. Recently, it has been proposed that IL-10 inhibits inducible nitric oxide synthase (iNOS) activity after myocardial I/R and consequently exerts cardioprotective effects. However, whether this actually occurs remains unclear. To test this hypothesis, we utilized iNOS-deficient (−/−), IL-10 −/−, and IL-10/iNOS −/− mice to examine the potential mechanism of IL-10-mediated cardioprotection after myocardial I/R. Wild-type, iNOS −/−, IL-10 −/−, and IL-10/iNOS −/− mice were subjected to in vivo myocardial ischemia (30 min) and reperfusion (24 h). Deficiency of iNOS alone did not significantly alter the extent of myocardial necrosis compared with wild-type mice. We found that deficiency of IL-10 resulted in a significantly ( P < 0.05) larger infarct size than that in wild-type hearts. Interestingly, deficiency of both IL-10 and iNOS yielded significantly ( P < 0.01) larger myocardial infarct sizes compared with wild-type animals. Histological examination of myocardial tissue samples revealed augmented neutrophil infiltration into the I/R myocardium of IL-10 −/− and IL-10/iNOS −/− mice compared with hearts of wild-type mice. These results demonstrate that 1) deficiency of endogenous IL-10 exacerbates myocardial injury after I/R; 2) the cardioprotective effects of IL-10 are not dependent on the presence or absence of iNOS; and 3) deficiency of IL-10 enhances the infiltration of neutrophils into the myocardium after I/R.
Optical measurement of cell-to-cell coupling in intact heart using subthreshold electrical stimulation
Authors: Akar Fadi G. , Roth Bradley J. , Rosenbaum David S.
Published: December 2017

Electrical coupling between myocytes plays a critical role in propagation, repolarization, and arrhythmias. On the basis of predictions from cable theory, we hypothesized that the cardiac space constant (λ) measured from the decay of subthreshold transmembrane potential (ST- V m) in space would provide an index of regional cell-to-cell coupling in the intact heart. With the use of voltage-sensitive dyes, the distribution of ST- V m was measured from hundreds of sites in close proximity to the site of subthreshold stimulation. λ was calculated from the exponential decay of ST- V min space. Consistent with known directional differences in axial resistance, the spatial distribution of ST- V mwas strongly dependent on fiber orientation, because λ was significantly ( P < 0.001) longer along (1.5 ± 0.1 mm) compared with across (0.8 ± 0.1 mm) fibers. There was a close linear relationship ( P < 0.001) between conduction velocity (CV) and λ along all fiber angles tested. Reducing gap junctional conductance by heptanol reversibly decreased CV and λ in parallel by ∼50%. In contrast, sodium channel blockade by flecainide slowed CV by 40% but had no effect on λ, reaffirming that λ was an index of passive but not active membrane properties. These data establish the feasibility of measuring λ as an index of cell-to-cell coupling in the intact heart, and indicate strong dependency of λ on fiber orientation and pharmacological alterations of gap junction conductance.
Selective blockade of mitochondrial KATPchannels does not impair myocardial oxygen consumption
Authors: Chen Yingjie , Traverse Jay H. , Zhang Jianyi , Bache Robert J.
Published: December 2017

Opening of mitochondrial ATP-sensitive potassium (KATP) channels has been postulated to prevent inhibition of respiration resulting from matrix contraction during high rates of ATP synthesis. Glibenclamide, which blocks KATP channels on the sarcolemma of vascular smooth muscle cells and myocardial myocytes as well as on the inner mitochondrial membrane, results in a decrease of myocardial oxygen consumption (MV˙o 2) both at rest and during exercise. This study examined whether this represents a primary effect of blockade of mitochondrial KATP channels or occurs secondary to coronary resistance vessel constriction with a decrease of coronary blood flow (CBF) and myocardial oxygen availability. MV˙o 2 was measured at rest and during treadmill exercise in 10 dogs during control conditions, after selective mitochondrial KATP channel blockade with 5-hydroxydecanoate (5-HD), and after nonselective KATPchannel blockade with glibenclamide. During control conditions, exercise resulted in progressive increases of CBF and MV˙o 2. Glibenclamide (50 μg · kg−1 · min−1 ic) resulted in a 17 ± 6% decrease of resting CBF with a downward shift of CBF during exercise and a decrease of coronary venous Po 2, indicating increased myocardial oxygen extraction. In contrast with the effects of glibenclamide, 5-HD (0.7 mg · kg−1 · min−1 ic) had no effect on CBF, MV˙o 2, or myocardial oxygen extraction. These findings suggest that glibenclamide decreased MV˙o 2 by causing resistance vessel constriction with a decrease of CBF and oxygen available to the myocardium rather than to a primary reduction of mitochondrial respiration.
Endogenous nitric oxide enhances coupling between O2consumption and ATP synthesis in guinea pig hearts
Authors: Shen Weiqun , Tian Rong , Saupe Kurt W. , Spindler Matthias , Ingwall Joanne S.
Published: December 2017

Endogenous nitric oxide (eNO) modulates tissue respiration. To test whether eNO modulates myocardial O2consumption (MV˙o2), ATP synthesis, and metabolic efficiency, we used isolated isovolumic guinea pig hearts perfused at a constant flow. Nω-nitro-l-arginine (l-NNA; 5 × 10−5mol/l) was used to inhibit eNO production. MV˙o2was measured at different levels of cardiac work, estimated as the rate-pressure product (RPP). ATP content and synthesis rate were determined using31P NMR and magnetization transfer during high cardiac work. l-NNA increased coronary vascular resistance (19 ± 3%, P < 0.05) and MV˙o2(12 ± 3%, P< 0.05) without an increase in the RPP. In contrast, vehicle infusion resulted in insignificant changes in coronary vascular resistance (3 ± 2%, P > 0.05) and MV˙o2(−2 ± 1%, P> 0.05). Compared with vehicle, l-NNA caused a higher MV˙o2both during KCl arrest (l-NNA 5.6 ± 0.5 vs. vehicle 3.0 ± 0.4 μmol · min−1· mg dry wt−1, P < 0.05) and during increased cardiac work elicited by elevating perfusate Ca2+, indicating an upward shift in the relationship between contractile performance (measured as RPP) and MV˙o2. However, neither ATP contents nor ATP synthesis rates were different in the two groups during high cardiac work. Thus, because inhibition of eNO production byl-NNA increased MV˙o2without a change in the ATP synthesis rate, these data suggest that eNO increases myocardial metabolic efficiency by reducing MV˙o2in the heart.
Complex AV nodal dynamics during ventricular-triggered atrial pacing in humans
Authors: Christini David J. , Stein Kenneth M. , Markowitz Steven M. , Mittal Suneet , Slotwiner David J. , Iwai Sei , Lerman Bruce B.
Published: December 2017

In vitro experiments have shown that the complexity of atrioventricular nodal (AVN) conduction dynamics increases with heart rate. Although complex AVN dynamics (e.g., alternans) have been observed clinically, human AVN dynamics during rapid pacing have not been systematically investigated. We studied such dynamics during ventricular-triggered atrial pacing in 37 patients with normal AVN function (18 patients with dual AVN pathway physiology and 19 patients without). Alternans, which always resulted from single pathway conduction, occurred in 18 patients. In 16 patients (3 of whom also had alternans), quasisinusoidal AVN conduction oscillations occurred (mean frequency 0.02 Hz); such oscillations have not been previously reported. There were no significant differences in the dynamics for patients with or without dual AVN pathways. To illuminate the governing dynamic mechanism, a second atrial pacing trial was performed on 12 patients after autonomic blockade. Blockade facilitated alternans but inhibited oscillations. This study suggests that rapid AVN excitation in vivo can lead to autonomically mediated AVN conduction oscillations or single pathway alternans that are a function of inherent nonlinear dynamic AVN tissue properties.
Nitric oxide-independent effects of tempol on sympathetic nerve activity and blood pressure in normotensive rats
Authors: Xu Hui , Fink Gregory D. , Chen Alex , Watts Stephanie , Galligan James J.
Published: December 2017

The role of the sympathetic nervous system in 4-hydroxy-2,2,6,6-tetramethyl piperidinoxyl (tempol)-induced cardiovascular responses in urethane-anesthetized, normotensive rats was evaluated. Tempol caused dose-dependent (30–300 μmol/kg iv) decreases in renal sympathetic nerve activity (RSNA), mean arterial blood pressure (MAP), and heart rate (HR). Similar responses were obtained after sinoaortic denervation and cervical vagotomy. These responses were not blocked following treatment with the nitric oxide synthase inhibitor NG-nitro-l-arginine (2.6 mg · kg−1· min−1iv for 5 min) or the α2-adrenergic receptor antagonist idazoxan (0.3 mg/kg iv bolus). Idazoxan blocked the effects of clonidine (10 μg/kg iv) on HR, MAP, and RSNA. Hexamethonium (30 mg/kg iv) inhibited RSNA, and tempol did not decrease RSNA after hexamethonium. The effects of tempol on HR and MAP were reduced by hexamethonium. In conclusion, depressor responses caused by tempol are mediated, partly, by sympathoinhibition in urethane-anesthetized, normotensive rats. Nitric oxide does not contribute to this response, and the sympathoinhibitory effect of tempol is not mediated via α2-adrenergic receptors. Finally, tempol directly decreases HR, which may contribute to the MAP decrease.
Pet CO2 inversely affects MSNA response to orthostatic stress
Authors: Shoemaker J. Kevin , O'Leary Debbie D. , Hughson Richard L.
Published: December 2017

Arterial hypocapnia has been associated with orthostatic intolerance. Therefore, we tested the hypothesis that hypocapnia may be detrimental to increases in muscle sympathetic nerve activity (MSNA) and total peripheral resistance (TPR) during head-up tilt (HUT). Ventilation was increased ∼1.5 times above baseline for each of three conditions, whereas end-tidal Pco 2 (Pet CO2 ) was clamped at normocapnic (Normo), hypercapnic (Hyper; +5 mmHg relative to Normo), and hypocapnic (Hypo; −5 mmHg relative to Normo) conditions. MSNA (microneurography), heart rate, blood pressure (BP, Finapres), and cardiac output (Q, Doppler) were measured continuously during supine rest and 45° HUT. The increase in heart rate when changing from supine to HUT ( P < 0.001) was not different across Pet CO2 conditions. MSNA burst frequency increased similarly with HUT in all conditions ( P < 0.05). However, total MSNA and the increase in total amplitude relative to baseline (%ΔMSNA) increased more when changing to HUT during Hypo compared with Hyper ( P < 0.05). Both BP and Q were higher during Hyper than both Normo and Hypo (main effect; P < 0.05). Therefore, the MSNA response to HUT varied inversely with levels of Pet CO2 . The combined data suggest that augmented cardiac output with hypercapnia sustained blood pressure during HUT leading to a diminished sympathetic response.
Src tyrosine kinase is the trigger but not the mediator of ischemic preconditioning
Authors: Hattori Reiji , Otani Hajime , Uchiyama Takamichi , Imamura Hiroji , Cui Jianhua , Maulik Nilanjana , Cordis Gerald A. , Zhu Li , Das Dipak K.
Published: December 2017

The signal cascade that triggers and mediates ischemic preconditioning (IPC) remains unclear. The present study investigated the role of the Src family of tyrosine kinases in IPC. Isolated and buffer-perfused rat hearts underwent IPC with three cycles of 5-min ischemia and 5-min reperfusion, followed by 30-min ischemia and 120-min reperfusion. The Src tyrosine kinase family-selective inhibitor PP1 was administered between 45 and 30 min before ischemia (early PP1 treatment) or for 15 min before IPC [early PP1-preconditioning (PC) treatment]. PP1 was also administered for 5 min before the sustained ischemia (late PP1 treatment) or after IPC (late PP1-PC treatment). Src kinase was activated after 30 min of ischemia in both the membrane and cytosolic fractions. Src kinase was also activated by IPC but was attenuated after the sustained ischemia. Early and late PP1 treatment inhibited Src activation after the sustained ischemia and reduced infarct size. Early PP1-PC inhibited Src activation after IPC but not after the sustained ischemia and blocked cardioprotection afforded by IPC. Late PP1-PC treatment abrogated IPC-induced activation of Src and protein kinase C (PKC)-ε in the membrane but not in the cytosolic fraction. This treatment modality abrogated Src activation after the sustained ischemia and failed to block cardioprotection afforded by IPC. These results suggest that Src kinase activation mediates ischemic injury but triggers IPC in the position either upstream of or parallel to membrane-associated PKC-ε.
Time course of forearm arterial compliance changes during reactive hyperemia
Authors: Baldassarre Damiano , Amato Mauro , Palombo Carlo , Morizzo Carmela , Pustina Linda , Sirtori Cesare R.
Published: December 2017

Ultrasonic studies have shown that arterial compliance increases after prolonged ischemia. The objective of the present study was to develop an alternative plethysmographic method to investigate compliance, exploring validity and clinical applicability. Forearm pulse volume (FPV) and blood pressure (BP) were used to establish the FPV-BP relationship. Forearm arterial compliance (FAC) was measured, and the area under the FAC-BP curve (FACAUC) was determined. The time course curve of compliance changes during reactive hyperemia was obtained by continuous measurements of FACAUCfor 20 s before and for 300 s after arterial occlusion. This technique allows us to effectively assess compliance changes during reactive hyperemia. Furthermore, the selected measurement protocol indicated the necessity for continuous measurements to detect “true” maximal FACAUCchanges. On multivariate analysis, preischemic FACAUCwas mainly affected by sex, peak FACAUCwas affected by sex and systolic BP, percent changes were affected by plasma high-density and low-density lipoprotein cholesterol, peak time was affected by age and body mass index, and descent time was affected by plasma triglyceride levels. The proposed technique is highly sensitive and well comparable with the generally accepted echotracking system. It may thus be considered as an alternative tool to detect and monitor compliance changes induced by arterial occlusion.
Altered SR protein expression associated with contractile dysfunction in diabetic rat hearts
Authors: Zhong Yan , Ahmed Saadia , Grupp Ingrid L. , Matlib Mohammed A.
Published: December 2017

The goal of this study was to examine whether alteration of sarcoplasmic reticulum (SR) protein levels is associated with early-onset diastolic and late-onset systolic dysfunction in streptozotocin (STZ)-induced diabetic rat hearts. Four-week diabetic rat hearts exhibited slow relaxation, whereas 6-wk diabetic rat hearts exhibited slow and depressed contraction. Total phospholamban level was increased, and phosphorylated level was decreased in 4- and 6-wk diabetic rat hearts. Sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA2) protein level was unchanged in 4-wk but decreased in 6-wk diabetic rat hearts. Only the apparent affinity of SR Ca2+uptake for Ca2+was decreased in 4-wk diabetic rat hearts, but the apparent affinity and the maximum rate was decreased in 6-wk diabetic rat hearts. Insulin treatment of the diabetic rats normalized SR protein expression and function. It was concluded that an increase in nonphosphorylated phospholamban and a decrease in the apparent affinity of SR Ca2+pump for Ca2+are associated with early-onset diastolic dysfunction and decreases in SERCA2 protein level and apparent affinity and maximum velocity of SR Ca2+pump are associated with late-onset systolic dysfunction in diabetic rats.
Beat-to-beat stroke volume estimation from aortic pressure waveform in conscious rats: comparison of models
Authors: Cerutti C. , Gustin M. P. , Molino P. , Paultre C. Z.
Published: December 2017

Several methods for estimating stroke volume (SV) were tested in conscious, freely moving rats in which ascending aortic pressure and cardiac flow were simultaneously (beat-to-beat) recorded. We compared two pulse-contour models to two new statistical models including eight parameters extracted from the pressure waveform in a multiple linear regression. Global as well as individual statistical models gave higher correlation coefficients between estimated and measured SV ( model 1, r = 0.97; model 2, r= 0.96) than pulse-contour models ( model 1, r = 0.83; model 2, r = 0.91). The latter models as well as statistical model 1 used the pulsatile systolic area and thus could be applied to only 47 ± 17% of the cardiac beats. In contrast, statistical model 2 used the pressure-increase characteristics and was therefore established for all of the cardiac beats. The global statistical model 2 applied to data sets independent of those used to establish the model gave reliable SV estimates: r= 0.54 ± 0.07, a small bias between −8% to +10%, and a mean precision of 7%. This work demonstrated the limits of pulse-contour models to estimate SV in conscious, unrestrained rats. A multivariate statistical model using eight parameters easily extracted from the aortic waveform could be applied to all cardiac beats with good precision.
Stress-activated protein kinase phosphorylation during cardioprotection in the ischemic myocardium
Authors: Fryer Ryan M. , Patel Hemal H. , Hsu Anna K. , Gross Garrett J.
Published: December 2017

Stress-activated protein kinases may be essential to cardioprotection. We assessed the role of p38 in an in vivo rat model of ischemia-reperfusion. Ischemic preconditioning (IPC) and the δ1-opioid receptor agonist 2-methyl-4aα-(3-hydroxyphenyl)-1,2,3,4,4a,5,12,12aα-octahydroquinolino [2,3,3-g]isoquinoline (TAN-67) significantly reduced infarct size (IS), expressed as a percentage of the area at risk (AAR), versus animals subjected only to 30 min of ischemia and 2 h of reperfusion (7.1 ± 1.5 and 29.6 ± 3.3 vs. 59.7 ± 1.6%). The p38 antagonist SB-203580 attenuated IPC when it was administered before (34.0 ± 6.9%) or after (25.0 ± 3.8%) the IPC stimulus; however, it did not significantly attenuate TAN-67-induced cardioprotection (39.6 ± 3.2). We also assessed the phosphorylation of p38 and c- junNH2-terminal kinase (JNK) throughout ischemia-reperfusion in nuclear and cytosolic fractions. After either intervention, no increase was detected in the phosphorylation state of either enzyme in the nuclear fraction or for p38 in the cytosolic fraction versus control hearts. However, there was a robust increase in JNK activity in the cytosolic fraction immediately on reperfusion that was more pronounced in animals subjected to IPC or administered TAN-67. These data suggest that SB-203580 likely attenuates IPC via the inhibition of kinases other than p38, which may include JNK. The data also suggest that activation of JNK during early reperfusion may be an important component of cardioprotection.
Existence of cardiac PNMT mRNA in adult rats: elevation by stress in a glucocorticoid-dependent manner
Authors: Križanová O. , Mičutková L. , Jeloková J. , Filipenko M. , Sabban E. , Kvetňanský R.
Published: December 2017

Phenylethanolamine N-methyltransferase (PNMT) is the enzyme that synthesizes epinephrine from norepinephrine. The aim of this study was to determine potential PNMT gene expression in the cardiac atria and ventricles of adult rats and to examine whether the gene expression of this enzyme is affected by immobilization stress. PNMT mRNA levels were detected in all four parts of the heart, with the highest level in the left atrium. Both Southern blot and sequencing verified the specificity of PNMT detected by RT-PCR. Single immobilization for 2 h increased gene expression of PNMT in both atria and ventricles. In atria, this effect was clearly modulated by glucocorticoids, because either adrenalectomy or hypophysectomy prevented the increase in PNMT mRNA levels in response to immobilization stimulus. This study establishes, for the first time, that PNMT gene expression occurs in cardiac atria and also, to a small extent, in ventricles of adult rats. Immobilization stress increases gene expression in atria and ventricles. This increase requires an intact hypothalamus-pituitary-adrenocortical axis, indicating the involvement of glucocorticoids.
TCA cycle kinetics in the rat heart by analysis of13C isotopomers using indirect1H[13C] detection
Authors: Carvalho R. A. , Zhao P. , Wiegers C. B. , Jeffrey F. M. H. , Malloy C. R. , Sherry A. D.
Published: December 2017

This study was designed to test the hypothesis that indirect1H[13C] detection of tricarboxylic acid (TCA) cycle intermediates using heteronuclear multiple quantum correlation-total correlation spectroscopy (HMQC-TOCSY) nuclear magnetic resonance (NMR) spectroscopy provides additional13C isotopomer information that better describes the kinetic exchanges that occur between intracellular compartments than direct13C NMR detection. NMR data were collected on extracts of rat hearts perfused at various times with combinations of [2-13C]acetate, propionate, the transaminase inhibitor aminooxyacetate, and13C multiplet areas derived from spectra of tissue glutamate were fit to a standard kinetic model of the TCA cycle. Although the two NMR methods detect different populations of13C isotopomers, similar values were found for TCA cycle and exchange fluxes by analyzing the two data sets. Perfusion of hearts with unlabeled propionate in addition to [2-13C]acetate resulted in an increase in the pool size of all four-carbon TCA cycle intermediates. This allowed the addition of isotopomer data from aspartate and malate in addition to the more abundant glutamate. This study illustrates that metabolic inhibitors can provide new insights into metabolic transport processes in intact tissues.
Endothelial dysfunction is induced by proinflammatory oxidant hypochlorous acid
Authors: Zhang Chunxiang , Patel Rakesh , Eiserich Jason P. , Zhou Fen , Kelpke Stacey , Ma Wenxin , Parks Dale A. , Darley-Usmar Victor , White C. Roger
Published: December 2017

The myeloperoxidase (MPO)-derived oxidant hypochlorous acid (HOCl) plays a role in tissue injury under inflammatory conditions. The present study tests the hypothesis that HOCl decreases nitric oxide (NO) bioavailability in the vasculature of Sprague-Dawley rats. Aortic ring segments were pretreated with HOCl (1–50 μM) followed by extensive washing. Endothelium-dependent relaxation was then assessed by cumulative addition of acetylcholine (ACh) or the calcium ionophore A23187 . HOCl treatment significantly impaired both ACh- and A23187 -mediated relaxation. In contrast, endothelium-independent relaxation induced by sodium nitroprusside was unaffected. The inhibitory effect of HOCl on ACh-induced relaxation was reversed by exposure of ring segments to l-arginine but notd-arginine. In cellular studies, HOCl did not alter endothelial NO synthase (NOS III) protein or activity, but inhibited formation of the NO metabolites nitrate (NO[Formula: see text]) and nitrite (NO[Formula: see text]). The reduction in total NO metabolite production in bovine aortic endothelial cells was also reversed by addition of l-arginine. These data suggest that HOCl induces endothelial dysfunction via modification ofl-arginine.
Impaired dilation of skeletal muscle microvessels to reduced oxygen tension in diabetic obese Zucker rats
Authors: Frisbee Jefferson C.
Published: December 2017

This study determined alterations to hypoxic dilation of isolated skeletal muscle resistance arteries (gracilis arteries; viewed via television microscopy) from obese Zucker rats (OZR) compared with lean Zucker rats (LZR). Hypoxic dilation was reduced in OZR compared with LZR. Endothelium removal and cyclooxygenase inhibition (indomethacin) severely reduced this response in both groups, although nitric oxide synthase inhibition ( N ω-nitro-l-arginine methyl ester) reduced dilation in LZR only. Treatment of vessels with a PGH2-thromboxane A2 receptor antagonist had no effect on hypoxic dilation in either group. Arterial dilation to arachidonic acid, iloprost, acetylcholine, and sodium nitroprusside was reduced in OZR versus LZR, although dilation to forskolin and aprikalim was unaltered. Treatment of arteries from OZR with oxidative radical scavengers increased dilation to hypoxia and agonists, with no effect on responses in LZR. The restored hypoxic dilation in OZR was abolished by indomethacin. These results suggest that hypoxic dilation of skeletal muscle microvessels from LZR represents the summated effects of prostanoid and nitric oxide release, whereas the impaired response of vessels in OZR may reflect scavenging of PGI2 by superoxide anion.
Requirement of protein tyrosine phosphatase SHP2 for NO-stimulated vascular smooth muscle cell motility
Authors: Brown Claire , Lin Yi , Hassid Aviv
Published: December 2017

We have previously reported that nitric oxide (NO) increases the motility of differentiated cultured primary aortic smooth muscle cells from adult rats. There is little information on the role of protein tyrosine phosphatases in vascular biology. One such phosphatase, Src homology 2 phosphatase 2 (SHP2), is essential for motility. We tested the hypothesis that NO increases SHP2 levels via a cGMP-mediated mechanism and that this effect is necessary for NO-stimulated cell motility. Here we report that two different NO donors increased SHP2 protein levels and enzyme activity. This effect was mimicked by several cGMP agonists and blocked by an inhibitor of guanylyl cyclase. Specific decrease of SHP2 protein levels via the use of antisense oligodeoxynucleotides (ODNs), but not several control ODNs attenuated the motogenic effect of NO, which indicates the involvement of SHP2 in NO-elicited motogenesis. S-nitroso- N-acetylpenicillamine failed to increase SHP2 protein levels in subcultured aortic smooth muscle cells. This provides a potential explanation for the lack of effect of NO on cell motility in dedifferentiated subcultured cells. These results support the hypothesis that NO-elicited upregulation of SHP2 via a cGMP-mediated pathway is necessary for NO-induced motogenesis in differentiated aortic smooth muscle cells.
Targeted deletion of A3adenosine receptors improves tolerance to ischemia-reperfusion injury in mouse myocardium
Authors: Cerniway Rachael J. , Yang Zequan , Jacobson Marlene A. , Linden Joel , Matherne G. Paul
Published: December 2017

A3adenosine receptors (A3ARs) have been implicated in regulating mast cell function and in cardioprotection during ischemia-reperfusion injury. The physiological role of A3ARs is unclear due to the lack of widely available selective antagonists. Therefore, we examined mice with targeted gene deletion of the A3AR together with pharmacological studies to determine the role of A3ARs in myocardial ischemia-reperfusion injury. We evaluated the functional response to 15-min global ischemia and 30-min reperfusion in isovolumic Langendorff hearts from A3AR−/−and wild-type (A3AR+/+) mice. Loss of contractile function during ischemia was unchanged, but recovery of developed pressure in hearts after reperfusion was improved in A3AR−/−compared with wild-type hearts (80 ± 3 vs. 51 ± 3% at 30 min). Tissue viability assessed by efflux of lactate dehydrogenase was also improved in A3AR−/−hearts (4.5 ± 1 vs. 7.5 ± 1 U/g). The adenosine receptor antagonist BW-A1433 (50 μM) decreased functional recovery following ischemia in A3AR−/−but not in wild-type hearts. We also examined myocardial infarct size using an intact model with 30-min left anterior descending coronary artery occlusion and 24-h reperfusion. Infarct size was reduced by over 60% in A3AR−/−hearts. In summary, targeted deletion of the A3AR improved functional recovery and tissue viability during reperfusion following ischemia. These data suggest that activation of A3ARs contributes to myocardial injury in this setting in the rodent. Since A3ARs are thought to be present on resident mast cells in the rodent myocardium, we speculate that A3ARs may have proinflammatory actions that mediate the deleterious effects of A3AR activation during ischemia-reperfusion injury.
Time course of collagen and decorin changes in rat cardiac and skeletal muscle post-MI
Authors: Zimmerman Scott D. , Thomas D. Paul , Velleman Sandra G. , Li Xia , Hansen Thomas R. , McCormick Richard J.
Published: December 2017

We examined the temporal relationship between messages (type I and type III mRNAs) for the principal fibrillar procollagens and subsequent collagen accretion, cross-linking, and decorin expression in the left ventricle (LV) postmyocardial infarction (post-MI). We sought to determine 1) what role the proteoglycan decorin plays in extracellular matrix (ECM) remodeling known to take place as a consequence of MI and 2) the extent skeletal muscle ECM is altered early post-MI. Therefore, after surgically induced production of small- to moderate-sized infarcts (∼20% of LV mass), extent and time course of ECM remodeling was evaluated in remaining viable LV free wall and in slow- [soleus (SOL)] and fast-twitch [gastrocnemius (GAST)] skeletal muscles. Decorin, collagen, and hydroxylysylpyridinium cross-link concentrations and α1(I) (type I) and α1(III) (type III) procollagen mRNAs were measured in LVs from noninfarcted controls and at 72 h, 1, 2, 5, and 13 wk post-MI. These same data were collected in SOL and GAST muscles at all time points except 13 wk. Type I procollagen mRNA increased at both 72-h and 1-wk time points in LVs. Type III procollagen mRNA was elevated at 1 wk, returning to baseline by 2 wk post-MI. Collagen concentration was significantly increased by 1 wk, more than doubled by 5 wk, and was elevated 129% by 13 wk in the remaining viable LV. LV decorin expression was unaltered at early time points, but increased 38% at 5 wk post-MI and doubled by 13 wk post-MI. In skeletal muscle, procollagen mRNAs were transiently altered in SOL and GAST muscles without any demonstrable effect on the measured ECM parameters. This study reports, for the first time, the upregulation time course of decorin and its relationship to increased HP cross-linking and accumulation of collagen in viable myocardium post-MI.
Tetrahydrobiopterin, a cofactor for NOS, improves endothelial dysfunction during chronic alcohol consumption
Authors: Sun Hong , Patel Kaushik P. , Mayhan William G.
Published: December 2017

We sought to investigate mechanisms that may account for impaired nitric oxide synthase (NOS)-dependent dilatation of cerebral arterioles during alcohol consumption. Our goals were to examine 1) the effect of exogenous application of a cofactor for NOS, i.e., tetrahydrobiopterin (BH4) on the reactivity of pial arterioles during alcohol consumption; and 2) endothelial NOS (eNOS) protein in nonalcohol-fed and alcohol-fed rats. Sprague-Dawley rats were fed liquid diets with or without alcohol for 2–3 mo. We measured in vivo diameter of pial arterioles in response to NOS-dependent agonists (ACh and ADP) and a NOS-independent agonist (nitroglycerin) before and during application of BH4. Blood vessels were then harvested for Western blot analysis of eNOS protein. In nonalcohol-fed rats, ACh and ADP produced vasodilatation, which was impaired in alcohol-fed rats. Vasodilatation to nitroglycerin was similar in both groups of rats. Application of BH4did not alter vasodilatation in nonalcohol-fed rats but improved impaired vasodilatation in alcohol-fed rats. Also, eNOS protein in cerebral cortex microvessels, the basilar artery, and aorta was not different between nonalcohol-fed and alcohol-fed rats. Thus impaired NOS-dependent vasodilatation during alcohol consumption does not appear to be related to an alteration in eNOS protein but may be related to a deficiency and/or alteration in the utilization of BH4.
Vagal cardiac function and arterial blood pressure stability
Authors: Wray D. Walter , Formes Kevin J. , Weiss Martin S. , O-Yurvati Albert H. , Raven Peter B. , Zhang Rong , Shi Xiangrong
Published: December 2017

This study was designed to investigate the importance of vagal cardiac modulation in arterial blood pressure (ABP) stability before and after glycopyrrolate or atropine treatment. Changes in R-R interval (RRI) and ABP were assessed in 10 healthy young (age, 22 ± 1.8 yr) volunteers during graded lower body negative pressure (LBNP) before and after muscarinic cholinergic (MC) blockade. Transient hypertension was induced by phenylephrine (1 μg/kg body wt), whereas systemic hypotension was induced by bilateral thigh cuff deflation after a 3-min suprasystolic occlusion. Power spectral densities of systolic [systolic blood pressure (SBP)] and diastolic ABP variability were examined. Both antimuscarinic agents elicited tachycardia similarly without significantly affecting baseline ABP. The increase in SBP after phenylephrine injection (+14 ± 2 mmHg) was significantly augmented with atropine (+26 ± 2 mmHg) or glycopyrrolate (+27 ± 3 mmHg) and associated with a diminished reflex bradycardia. The decrease in SBP after cuff deflation (−9.2 ± 1.2 mmHg) was significantly greater after atropine (−15 ± 1 mmHg) or glycopyrrolate (−14 ± 1 mmHg), with abolished reflex tachycardia. LBNP significantly decreased both SBP and RRI. However, after antimuscarinic agents, the reduction in SBP was greater ( P < 0.05) and was associated with less tachycardia. Antimuscarinic agents reduced ( P < 0.05) the low-frequency (LF; 0.04–0.12 Hz) power of ABP variability at rest. The LF SBP oscillation was significantly augmented during LBNP, which was accentuated ( P < 0.05) after antimuscarinic agents and was correlated ( r = −0.79) with the decrease in SBP. We conclude that antimuscarinic agents compromised ABP stability by diminishing baroreflex sensitivity, reflecting the importance of vagal cardiac function in hemodynamic homeostasis. The difference between atropine and glycopyrrolate was not significant.
Cardiac performance as a function of intracellular oxygen tension in buffer-perfused hearts
Authors: Schenkman Kenneth A.
Published: December 2017

Critical intracellular myocardial oxygen tension was determined by optical spectroscopic measurement of myoglobin oxygen saturation in crystalloid-perfused guinea pig hearts. Accurate end-point determinations of the maximally oxygenated and deoxygenated myoglobin were made. Hearts were subjected to a steady decrease in perfusate oxygen tension while left ventricular developed pressure, maximal left ventricular dP/d t, myocardial oxygen consumption, lactate release, and adenosine release were measured as indices of myocardial function. Intracellular myoglobin was found to be only 72% saturated under baseline conditions with an arterial oxygen tension of >600 mmHg at 37°C. Baseline intracellular oxygen tension was 6.3 mmHg. Myocardial oxygen consumption was decreased by 10% when the oxygen tension fell to 5.7 mmHg, and cardiac contraction decreased 10% when oxygen tension was 4.1 mmHg. Adenosine release and, finally, lactate release began to increase at sequentially lower oxygen tensions. The present results indicate that the buffer-perfused guinea pig heart at 37°C has an intracellular oxygen tension just above the threshold for impaired function.
Intact osmoregulatory centers in the preterm ovine fetus: Fos induction after an osmotic challenge
Authors: Caston-Balderrama A. , Nijland M. J. M. , McDonald T. J. , Ross M. G.
Published: December 2017

We previously demonstrated a functional systemic dipsogenic response in the near-term fetal sheep (128–130 days; 145 days = full-term) with swallowing activity stimulated in response to central and systemic hypertonic saline. Preterm fetal sheep (110–115 days) do not consistently demonstrate swallowing in response to hypertonic stimuli, and it is unclear whether this is due to immaturity of osmoreceptor mechanisms or neuronal pathways activating swallowing motor neurons. To determine whether osmoreceptive regions in the preterm fetus are activated by changes in plasma tonicity, we examined Fos expression with immunostaining in these neurons in response to an osmotic challenge. Nine preterm fetal sheep [five hypertonic saline-treated fetuses (Hyp) and four isotonic saline-treated fetuses (Iso)] were prepared with vascular and intraperitoneal catheters. Seventy-five minutes before tissue collection, hypertonic (1.5 M) or isotonic saline was infused (12 ml/kg) via an intraperitoneal catheter to fetuses. Brains were examined for patterns of neuronal activation (demonstrated by Fos protein expression). Hyp demonstrated increases in plasma osmolality (∼10 mosmol/kg H2O) and Na concentrations (5 meq/l). Increased Fos expression was detected in Hyp in the organum vasculosum of the lamina terminalis (OVLT), subfornical organ (SFO), median preoptic nucleus (MnPO), supraoptic (SON), and paraventricular nuclei (PVN) compared with Iso animals. Neuronal activation within the OVLT, SFO, and MnPO indicates intact osmoregulatory mechanisms, whereas activation of the SON and PVN suggests intact fetal neural pathways to arginine vasopressin neurons. These results suggest that preterm fetal swallowing insensitivity to osmotic stimuli may be due to immaturity of integrated motor neuron pathways.
Women at altitude: forearm hemodynamics during acclimatization to 4,300 m with α1-adrenergic blockade
Authors: Zamudio Stacy , Douglas Matthew , Mazzeo Robert S. , Wolfel Eugene E. , Young David A. , Rock Paul B. , Braun Barry , Muza Stephen R. , Butterfield Gail E. , Moore Lorna G.
Published: December 2017

We hypothesized that blockade of α1-adrenergic receptors would prevent the rise in peripheral vascular resistance that normally occurs during acclimatization. Sixteen eumenorrheic women were studied at sea level (SL) and at 4,300 m ( days 3 and 10). Volunteers were randomly assigned to take the selective α1-blocker prazosin or placebo. Venous compliance, forearm vascular resistance, and blood flow were measured using plethysmography. Venous compliance fell by day 3 in all subjects (1.39 ± 0.30 vs. 1.62 ± 0.43 ml · Δ30 mmHg−1 · 100 ml tissue−1 · min−1 at SL, means ± SD). Altitude interacted with prazosin treatment ( P < 0.0001) such that compliance returned to SL values by day 10in the prazosin-treated group (1.68 ± 0.19) but not in the placebo-treated group (1.20 ± 0.10, P < 0.05). By day 3 at 4,300 m, all women had significant falls in resistance (35.2 ± 13.2 vs. 54.5 ± 16.1 mmHg · ml−1 · min−1 at SL) and rises in blood flow (2.5 ± 1.0 vs. 1.6 ± 0.5 ml · 100 ml tissue−1 · min−1at SL). By day 10, resistance and flow returned toward SL, but this return was less in the prazosin-treated group (resistance: 39.8 ± 4.6 mmHg · ml−1 · min−1 with prazosin vs. 58.5 ± 9.8 mmHg · ml−1 · min−1 with placebo; flow: 1.9 ± 0.7 ml · 100 ml tissue−1 · min−1 with prazosin vs. 2.3 ± 0.3 ml · 100 ml tissue−1 · min−1 with placebo, P < 0.05). Lower resistance related to higher circulating epinephrine in both groups ( r = −0.50, P < 0.0001). Higher circulating norepinephrine related to lower venous compliance in the placebo-treated group ( r = −0.42, P < 0.05). We conclude that α1-adrenergic stimulation modulates peripheral vascular changes during acclimatization.
Beneficial effects of the Ca2+sensitizer levosimendan in human myocardium
Authors: Brixius Klara , Reicke Sebastian , Schwinger Robert H. G.
Published: December 2017

Levosimendan has been reported to increase cardiac Ca2+sensitivity, thereby not enhancing intracellular Ca2+or diastolic tension. This may be advantageous for the treatment of heart failure patients. Therefore, the present study investigates the mode of action of levosimendan in both failing and nonfailing (NF) human myocardium. The effects of levosimendan on contractile force, Ca2+transient (fura 2), and the force-frequency relationship (0.5–3 Hz) were studied in left ventricular terminally failing [dilated cardiomyopathy (DCM; n = 18)] and nonfailing (NF) myocardium (donor hearts, n = 6). Levosimendan (0.03–10 μmol/l) increased contractile force in NF (EC50: 0.38 μmol/l). In left ventricular failing myocardium, levosimendan only increased force after prestimulation with isoprenaline (0.1 μmol/l, EC50levosimendan: 0.062 μmol/l) or after elevation of the extracellular Ca2+concentration from 1.8 to 3.2 mmol/l. After application of isoprenaline, levosimendan shortened relaxation and contraction kinetics. Levosimendan did not change the systolic Ca2+transient but it improved the force-frequency relationship in DCM. In conclusion, levosimendan improves contraction in failing human myocardium under conditions with already increased intracellular Ca2+.
Differential responses of newborn pulmonary arteries and veins to atrial and C-type natriuretic peptides
Authors: Tolsa Jean-Francois , Gao Yuansheng , Sander Fred C. , Souici Anne-Christine , Moessinger Adrien , Raj J. Usha
Published: December 2017

Atrial natriuretic peptide (ANP) and C-type natriuretic peptide (CNP) are important dilators of the pulmonary circulation during the perinatal period. We compared the responses of pulmonary arteries (PA) and veins (PV) of newborn lambs to these peptides. ANP caused a greater relaxation of PA than of PV, and CNP caused a greater relaxation of PV than of PA. RIA showed that ANP induced a greater increase in cGMP content of PA than CNP. In PV, ANP and CNP caused a similar moderate increase in cGMP content. Receptor binding study showed more specific binding sites for ANP than for CNP in PA and more for CNP than for ANP in PV. Relative quantitative RT-PCR for natriuretic peptide receptor A (NPR-A) and B (NPR-B) mRNAs show that, in PA, NPR-A mRNA is more prevalent than NPR-B mRNA, whereas, in PV, NPR-B mRNA is more prevalent than NPR-A mRNA. In conclusion, in the pulmonary circulation, arteries are the major site of action for ANP, and veins are the major site for CNP. Furthermore, the differences in receptor abundance and the involvement of a cGMP-independent mechanism may contribute to the heterogeneous effects of the natriuretic peptides in PA and PV of newborn lambs.
Effects of uniform electric fields on intracellular calcium transients in single cardiac cells
Authors: Sharma Vinod , Tung Leslie
Published: December 2017

Although intracellular calcium ([Ca2+]i) transients in cardiac cells have been well studied in the uniformly polarized cell membrane, how these transients are modified during field stimulation when the cell membrane is nonuniformly polarized has not been investigated. In this study we characterized the effects of uniform field stimuli on [Ca2+]itransients in isolated guinea pig cardiac cells. Single guinea pig cells were enzymatically isolated, loaded with the [Ca2+]ifluorescent indicator fluo-3, and stimulated along their longitudinal axes with S1 or S1-S2 (S1-S2 = 50 ms) pulses. The fluorescence signals were recorded simultaneously from up to 12 sites along the cell length using a multisite mapping system. S1 pulse, applied during the resting phase of the action potential, induced [Ca2+]itransients that had an earlier onset at the anodal-facing end, suggesting that [Ca2+]igradients (∇[Ca2+]i) develop during the rising phase of the [Ca2+]itransients. With the assumption that the peak change in [Ca2+]iis 980 nM, ∇[Ca2+]iwas estimated to be ∼3.4 nM/μm in the anodal half of the cell for a nominal 10 V/cm field and negligible in the cathodal half. The S2 pulse that was applied during the plateau of the action potential also perturbed the [Ca2+]itransients and produced [Ca2+]igradients directed from the center to either end of the cell. Mean ∇[Ca2+]iin the anodal half of the cell (∼4.2 nM/μm) was found to be statistically higher than in the cathodal half (∼2.8 nM/μm).
Electrolyte levels of rat salivary secretions in relation to fluid-flow rate
Authors: Schneyer C. A. , Schneyer L. H.
Published: December 2017

Rat parotid, submaxillary and sublingual salivas, collected directly from the respective gland ducts following a single stimulatory dose of pilocarpine, show widely divergent Na and K concentrations at high flow rates. Parotid secretion shows high Na and low K levels; submaxillary, low Na and high K; sublingual has intermediate levels of both electrolytes. Changes in flow rate and duration of secretion modify Na-K balance. With decreasing flow rate and increasing duration of flow, Na level of parotid secretion decreases, whereas Na of submaxillary increases before decreasing. Concurrently, K in these secretions first shows a transient elevation followed by a decrease and subsequent increase. Parotid saliva is usually isotonic or slightly hypertonic to serum at high flow rates; submaxillary and sublingual secretions are generally hypotonic at all flow rates. Some correlation between electrolyte levels of gland and secretion seems apparent.
Vitamin B12 absorption in rats, studied by a ‘loop’ technique
Authors: Okuda Kunio
Published: December 2017

A technique to prepare an intestinal loop in situ in rats is described for the study of the effect of intrinsic factor (IF) on the absorption of vitamin B12 and of the site of absorption. It was found that a) the site of absorption of vitamin B12 is the smal intestine and, particularly, the middle portion; b) a saline extract of rat stomach mucosa, as well as rat gastric juice, when mixed with a low test dose of vitamin B12, markedly increased the absorption of vitamin B12 by the loop. A quantitative relationship was demonstrated between absorption and vitamin B12-binding power of such an extract. However, a purified hog IF did not enhance the absorption of vitamin B12 and c) two different mechanisms for the absorption of vitamin B12 are suggested. One operates when a small physiological dose is administered; the absorption can be enhanced by co-administration of IF and be inhibited by ethylenediaminetetraacetate (EDTA). The other operates when a high dose is given; the absorption under such conditions is not affected either way by the administration of IF or EDTA.
Relation of anterior pituitary function to aldosterone and corticosterone secretion in conscious dogs
Authors: Davis James O. , Carpenter Charles C. J. , Ayers Carlos R. , Baiin Robert C.
Published: December 2017

Secretion of aldosterone and corticosterone was studied in conscious dogs by means of a chronic indwelling catheter to obtain adrenal vein blood. In most conscious normal dogs, steroid secretion was lower than in anesthetized normal animals following acute adrenolumber vein cannulation. However, in dogs not well trained or excitable, secretion of aldosterone and corticosterone was strikingly elevated above the basal output. This finding probably reflects an increased plasma level of ACTH. In dogs with thoracic caval constriction, aldosterone output was markedly increased above normal whereas corticosterone and Porter Silber chromogen secretion was frequently very low, a finding which suggests a normal plasma level of ACTH. Hypophysectomy of dogs with caval constriction resulted in a greater, more abrupt fall in corticosterone than in aldosterone secretion. In two of these dogs, aldosterone secretion fell to normal or below within 2 days, whereas in the other two dogs, aldosterone output, although reduced, remained above normal for several days. Porter Silber chromogens showed changes similar to those observed for corticosterone. It is concluded that the anterior pituitary provided important support for increased aldosterone production but was unessential for hypersecretion of aldosterone.