bluuebunny/crossref_metadata_2025 huggingface dataset:
Spectral analysis of heart rate, arterial pressure, and muscle sympathetic nerve activity in normal humans
Authors: Nakata Akio , Takata Shigeo , Yuasa Toyoshi , Shimakura Atsuhiro , Maruyama Michiro , Nagai Hideo , Sakagami Satoru , Kobayashi Ken-Ichi
Published: December 2017

We investigated the frequency components of fluctuations in heart rate, arterial pressure, respiration, and muscle sympathetic nerve activity (MSNA) in 11 healthy women using an autoregressive model and examined the relation among variables using Akaike’s relative power contribution analysis with multivariate autoregressive model fitting. Power spectral analysis of MSNA revealed two peaks, with low-frequency (LF) and high-frequency (HF) components. The LF component of MSNA was a major determinant of the LF component of arterial pressure and R-R interval variability (0.70 ± 0.07 and 0.18 ± 0.05, respectively). The effect of the LF component of MSNA on arterial pressure showed no change in response to propranolol but was diminished (0.35 ± 0.08) by phentolamine ( P < 0.02). The effect of the LF component of MSNA on R-R interval was not altered by pharmacological sympathetic nerve blockade. The HF component of MSNA did not influence other variables but was influenced by R-R interval, arterial pressure, and respiration. These findings indicate that the LF component of MSNA reflects autonomic oscillations, whereas the HF component is passive and influenced by other cardiovascular variables.
Energy provision from glycogen, glucose, and fatty acids on adrenergic stimulation of isolated working rat hearts
Authors: Goodwin Gary W. , Ahmad Faisal , Doenst Torsten , Taegtmeyer Heinrich
Published: December 2017

We postulated that glycogen is a significant energy substrate compared with fatty acids and glucose in response to adrenergic stimulation of working rat hearts. Oxidation rates were determined at 1-min intervals by release of3H2O from [9,10-3H]oleate (0.4 mM, 1% albumin) and14CO2from exogenous [U-14C]glucose (5 mM) or, by a pulse-chase method, from [14C]glycogen. We estimated the14C enrichment of glycogen metabolized at each time point to determine true rates of glycogen use. Based on the pattern of glycogen enrichment over time, glycogenolysis did not exhibit a high degree of preference for newly synthesized glycogen. Epinephrine (1 μM) increased contractile performance 86% but did not stimulate oleate oxidation. The increased energy demand was supplied by carbohydrates, initially by a burst of glycogenolysis (contributing 35% to total ATP synthesis for 5 min) and followed by delayed increase in the use of exogenous glucose (eventually contributing 29% to ATP synthesis). On the basis of the release of14CO2and [14C]lactate specifically from glucose or glycogen, we found that a larger portion of glycogen was oxidized compared with exogenous glucose, augmenting the yield of ATP from glycogen. Thus the heart responds to an acute increase in energy demand by selective oxidation of glycogen.
A new method to measure regional myocardial time-varying elastance using minute vibration
Authors: Shishido Toshiaki , Sugimachi Masaru , Kawaguchi Osamu , Miyano Hiroshi , Kawada Toru , Matsuura Wataru , Ikeda Yasuhiro , Sato Takayuki , Alexander Joe , Sunagawa Kenji
Published: December 2017

We developed a new technique to evaluate regional myocardial elastance using minute vibration. In 13 isolated cross-circulated canine hearts, we applied small sinusoidal vibrations of displacement to the left ventricular surface at various frequencies (50–100 Hz). Using the measured displacement and force between the vibrator head and myocardium, we derived myocardial elastance on the basis of the equation of motion for a given moment of the cardiac cycle. Simultaneous solution of the equations of motion at different frequencies yielded a unique value of elastance. Time-varying myocardial elastance increased from diastole (0.028 ± 0.211 × 106 dyn/cm) to systole (0.833 ± 0.391 × 106 dyn/cm). The end-systolic elastance ( e es) linearly correlated with end-systolic left ventricular elastance ( r = 0.717, P < 0.001) and also with the end-systolic Young’s modulus ( r = 0.874, P < 0.0001). We also measured e es at both ischemic and nonischemic regions during coronary occlusion. Young’s modulus, estimated by normalizing e es by the wall thickness and by the estimated mass, did not change significantly at the nonischemic regions, whereas it decreased significantly from 2.303 ± 0.556 to 1.173 ± 0.370 × 106dyn/cm2 at the ischemic region after coronary occlusion ( P < 0.005). We conclude that this technique is useful for the quantitative assessment of regional myocardial elastance.
NO decreases phosphorylation of focal adhesion proteins via reduction of Ca in rat aortic smooth muscle cells
Authors: Kaur Kuljeet , Yao Jian , Pan Xiaolei , Matthews Carolyn , Hassid Aviv
Published: December 2017

Our laboratory has previously reported that the antimitogenic effect of nitric oxide (NO) in primary cultures of rat aortic smooth muscle cells may be attributed to activation of protein tyrosine phosphatase and dephosphorylation of protein phosphotyrosine [G. S. Dhaunsi, C. Matthews, K. Kaur, and A. Hassid. Am. J. Physiol. 272 ( Heart Circ. Physiol. 41): H1342–H1349, 1997]. The goal of the current study was to investigate the role of cytoplasmic Ca in this process and to identify protein substrates that are dephosphorylated by treatment with NO. Treatment of primary rat aortic smooth muscle cell cultures with the NO donor S-nitroso- N-acetylpenicillamine (SNAP) decreased cytoplasmic Ca levels and elicited phosphotyrosine dephosphorylation. Both effects were mimicked by the extracellular and intracellular Ca chelators ethylene glycol-bis(β-aminoethyl ether)- N, N, N′, N′-tetraacetic acid (EGTA) and 1,2-bis(2-aminophenoxy)ethane- N, N, N′, N′-tetraacetic acid (BAPTA), respectively, and by the Ca channel blocker nifedipine. Conversely, elevation of cytoplasmic Ca via the use of the Ca ionophore A-23187 or high extracellular K+prevented or attenuated SNAP-induced dephosphorylation. Both BAPTA and nifedipine also decreased DNA synthesis, providing further evidence to link dephosphorylation to antimitogenesis. Two of the proteins dephosphorylated by treatment of cells with NO or EGTA were identified as the focal adhesion proteins, cortactin and paxillin. These results indicate that NO-induced dephosphorylation of protein phosphotyrosine is mediated by reduction of cytoplasmic Ca and suggest that dephosphorylation of focal adhesion proteins may be of relevance to the antimitogenic effect of NO.
Neutrophil elastase promotes lung microvascular injury and proteolysis of endothelial cadherins
Authors: Carden D. , Xiao F. , Moak Candace , Willis Bradley H. , Robinson-Jackson Sherry , Alexander Steve
Published: December 2017

Intestinal ischemia-reperfusion (I-R) is associated with lung injury and the acute respiratory distress syndrome. The hypothesis of this study was that intestinal I-R activates circulating neutrophils to promote elastase-mediated lung injury. Isolated rat lungs were perfused with blood or plasma obtained after intestinal I-R, and lung neutrophil retention and injury and bronchoalveolar lavage (BAL) elastase were measured. Perfusion with I-R blood caused lung neutrophil accumulation and injury and increased BAL elastase. These effects were attenuated by the elastase inhibitor L-658758. Interference with neutrophil adherence before gut reperfusion blocked BAL elastase accumulation. The role of endothelial junction proteins (cadherins) in I-R-elicited lung damage was also evaluated. Activated human neutrophils proteolyzed cadherins in human umbilical vein endothelial cells. Furthermore, plasma of patients with acute respiratory distress syndrome contained soluble cadherin fragments. The results of this study suggest that the elastase released by systemically activated neutrophils contributes to lung neutrophil accumulation and pulmonary microvascular injury. Elastase-mediated proteolysis of endothelial cell cadherins may represent the mechanism through which lung microvascular integrity is disrupted after intestinal I-R.
Delayed reduction of tissue water diffusion after myocardial ischemia
Authors: Hsu Edward W. , Xue Rong , Holmes Alex , Forder John R.
Published: December 2017

The apparent diffusion coefficient (ADC) of water after regional myocardial ischemia was measured in isolated, perfused rabbit hearts by using magnetic resonance imaging (MRI) techniques. After ligation of the left anterior descending coronary artery, the ADC of the nonperfused region showed a gradual but significant decreasing trend over time, whereas that of the normally perfused myocardium remained constant. Morphological analysis revealed that the ADC decrease reflected the expansion of a subregion of reduced ADC within the nonperfused myocardium. The dynamics of the diffusion change and the morphological progression of the affected tissue suggest that the ADC decrease may be linked to the onset of myocardial infarction, which is known to involve myocyte swelling. The ADC reduction provides a potentially valuable MRI tissue-contrast mechanism for noninvasively determining the viability of the ischemic myocardium and assessing the dynamics of acute myocardial infarction.
Increased expression of glomerular AT1 receptors in rats with myocardial infarction
Authors: Mento Peter F. , Pica Mary E. , Hilepo Jim , Chang Jaime , Hirsch Larissa , Wilkes Barry M.
Published: December 2017

Rats with congestive heart failure demonstrate striking intrarenal vasoconstriction that contributes to reduced renal excretory function. We previously demonstrated that inhibition of angiotensin action reverses intrarenal vasoconstriction in rats 4–6 wk after coronary artery ligation. In the present study we tested the hypothesis that abnormalities in the expression and regulation of glomerular angiotensin receptors contribute to the intrarenal vasoconstriction. Because glomerular angiotensin type 1 (AT1) receptors normally downregulate in response to high local ANG II concentrations, we anticipated that glomerular AT1-receptor expression would be reduced in rats after myocardial infarction (MI). To our surprise, the density of glomerular AT1receptors was nearly double (97% increase, P < 0.002) that of controls, indicating an acquired abnormality in angiotensin receptor regulation. This was specific for renal glomeruli, because the density of angiotensin receptors on renal vasculature was decreased in rats after MI compared with normal controls. Glomerular AT1-receptor expression was downregulated by an acute pharmacological infusion of ANG II and upregulated by acute angiotensin-converting enzyme inhibition to a similar extent in MI and control rats. Renal cortical mRNA expression showed an increase in the renin mRNA-to-actin ratio and angiotensinogen-to-actin ratio, indicating stimulation of the intrarenal angiotensin system in rats after MI. The data indicate a specific dysregulation of AT1receptors in glomeruli but not blood vessels after MI.
Assessment of glycogen turnover in aerobic, ischemic, and reperfused working rat hearts
Authors: Fraser Heather , Lopaschuk Gary D. , Clanachan Alexander S.
Published: December 2017

Glycogen and its turnover are important components of myocardial glucose metabolism that significantly impact on postischemic recovery. We developed a method to measure glycogen turnover (rates of glycogen synthesis and degradation) in isolated working rat hearts using [3H]- and [14C]glucose. In aerobic hearts perfused with 11 mM glucose, 1.2 mM palmitate, and 100 μU/ml insulin, rates of glycogen synthesis and degradation were 1.24 ± 0.3 and 0.53 ± 0.25 μmol ⋅ min−1⋅ g dry wt−1, respectively. Low-flow ischemia (0.5 ml/min, 60 min) elicited a marked glycogenolysis; rates of glycogen synthesis and degradation were 0.54 ± 0.16 and 2.12 ± 0.14 μmol ⋅ min−1⋅ g dry wt−1, respectively. During reperfusion (30 min), mechanical function recovered to 20% of preischemic values. Rates of synthesis and degradation were 1.66 ± 0.16 and 1.55 ± 0.21 μmol ⋅ min−1⋅ g dry wt−1, respectively, and glycogen content remained unchanged (25 ± 3 μmol/g dry wt). The assessment of glycogen metabolism needs to take into account the simultaneous synthesis and degradation of glycogen. With this approach, a substantial turnover of glycogen was detectable not only during aerobic conditions but also during ischemia as well as reperfusion.
Demonstration of nonlinear components in heart rate variability of healthy persons
Authors: Braun Christian , Kowallik Peter , Freking Ansgar , Hadeler Dörte , Kniffki Klaus-Dietrich , Meesmann Malte
Published: December 2017

We present a systematic approach for detecting nonlinear components in heart rate variability (HRV). The analysis is based on twenty-three 48-h Holter recordings in healthy persons during sinus rhythm. Although many segments of 1,024 R-R intervals are stationary, only few stationary segments of 8,192–32,768 R-R intervals can be found using a test of Isliker and Kurths ( Int. J. Bifurcation Chaos 3:1573–1579, 1993.). By comparing the correlation integrals from these segments and corresponding surrogate data sets, we reject the null hypothesis that these time series are realization of linear processes. On the basis of a test statistic exploring the differences of consecutive R-R intervals, we reject the hypothesis that the R-R intervals represent a static transformation of a linear process using optimized surrogate data. Furthermore, time irreversibility of the heartbeat data is demonstrated. We interpret these results as a strong evidence for nonlinear components in HRV. Thus R-R intervals from healthy persons contain more information than can be extracted by linear analysis in the time and frequency domain.
Quantitative assessment of [Ca2+]ilevels in rat skeletal muscle in vivo
Authors: Tóth András , Ivanics Tamás , Ruttner Zoltán , Slaaf Dick W. , Reneman Robert S. , Ligeti László
Published: December 2017

Intracellular free Ca2+concentration ([Ca2+]i) plays an essential role in physiological regulatory processes and common pathological conditions. Better understanding of these phenomena is still hampered by problems encountered in the quantitative assessment of [Ca2+]ichanges, especially in blood-perfused organs. This study demonstrates that the ratiometric fluorescence technique can be adapted for quantitative in vivo [Ca2+]ideterminations. The rat spinotrapezius muscle was topically loaded with indo 1-AM and imaged by a cooled digital camera. Ratio images were calculated in small regions (100 μm × 100 μm) practically devoid of large vessels in the resting state, after 30 min of ischemia, 20 min of reperfusion, or ionomycin or manganate treatments. When we assumed an average [Ca2+]iof 100 nM in the resting blood-perfused muscle, ischemia increased [Ca2+]ito ∼200 nM. During reperfusion [Ca2+]idecreased to ∼140 nM. Ionomycin induced an increase in [Ca2+]ito well above 750 nM. Manganate reduced Ca2+-dependent fluorescence to virtually zero. Our main conclusion is that changes in [Ca2+]ican be monitored and quantitatively determined in vivo.
Role of adenosine in the regulation of coronary blood flow in swine at rest and during treadmill exercise
Authors: Duncker Dirk J. , Stubenitsky René , Verdouw Pieter D.
Published: December 2017

A pivotal role for adenosine in the regulation of coronary blood flow is still controversial. Consequently, we investigated its role in the regulation of coronary vasomotor tone in swine at rest and during graded treadmill exercise. During exercise, myocardial O2 consumption increased from 167 ± 18 μmol/min at rest to 399 ± 27 μmol/min at 5 km/h ( P ≤ 0.05), which was paralleled by an increase in O2 delivery, so that myocardial O2 extraction (76 ± 1 and 78 ± 1% at rest and 5 km/h, respectively) and coronary venous[Formula: see text] (24.5 ± 1.0 and 22.8 ± 0.3 mmHg at rest and 5 km/h, respectively) remained unchanged. After adenosine receptor blockade with 8-phenyltheophylline (5 mg/kg iv), the relation between myocardial O2consumption and coronary vascular resistance was shifted toward higher resistance, whereas myocardial O2extraction rose to 81 ± 1 and 83 ± 1% at rest and 5 km/h and coronary venous [Formula: see text] fell to 19.2 ± 0.8 and 18.9 ± 0.8 mmHg at rest and 5 km/h, respectively (all P ≤ 0.05). Thus, although adenosine is not mandatory for the exercise-induced coronary vasodilation, it exerts a vasodilator influence on the coronary resistance vessels in swine at rest and during exercise.
Deformation-induced ATP release from red blood cells requires CFTR activity
Authors: Sprague Randy S. , Ellsworth Mary L. , Stephenson Alan H. , Kleinhenz Mary E. , Lonigro Andrew J.
Published: December 2017

Recently, it was reported that rabbit and human red blood cells (RBCs) release ATP in response to mechanical deformation. Here we investigate the hypothesis that the activity of the cystic fibrosis transmembrane conductance regulator (CFTR), a member of the ATP binding cassette, is required for deformation-induced ATP release from RBCs. Incubation of rabbit RBCs with either of two inhibitors of CFTR activity, glibenclamide (10 μM) or niflumic acid (20 μM), resulted in inhibition of deformation-induced ATP release. To demonstrate the contribution of CFTR to deformation-induced ATP release from human RBCs, cells from healthy humans, patients with cystic fibrosis (CF), or patients with chronic obstructive lung disease (COPD) unrelated to CF were studied. RBCs of healthy humans and COPD patients released ATP in response to mechanical deformation. In contrast, deformation of RBCs from patients with CF did not result in ATP release. We conclude that deformation-induced ATP release from rabbit and human RBCs requires CFTR activity, suggesting a previously unrecognized role for CFTR in the regulation of vascular resistance.
pHi and pHo at different depths in perfused myocardium measured by confocal fluorescence microscopy
Authors: Muller-Borer Barbara J. , Yang Hua , Marzouk Sayed A. M. , Lemasters John J. , Cascio Wayne E.
Published: December 2017

Confocal microscopy and the H+-sensitive fluorophore carboxyseminaphthorhodafluor-1 (SNARF-1) were used to measure either intracellular pH (pHi) or extracellular pH (pHo) in isolated, arterially perfused rabbit papillary muscles. Single-excitation, dual-emission fluorescent images of the endocardial surface and underlying myocardium to a depth of 300 μm were simultaneously recorded from perfused cylindrical muscles suspended in a controlled atmosphere oriented oblique to the focal plane. Contraction was inhibited by the addition of butanedione monoxime. In separate muscles, pHo was measured during continuous perfusion of SNARF-1 free acid. pHi measurements were made after the muscle was loaded with SNARF-1/AM and the extracellular space was cleared of residual fluorophore. Initial experiments demonstrated the uniformity of ratiometric measurements as a function of pH, image depth, and fluorophore concentration, thereby establishing the potential feasibility of this method for quantitative intramural pH measurements. In subsequent experiments, the method was validated in isolated, arterially perfused rabbit papillary muscle during normal arterial perfusion and as pHi and pHo were altered by applying CO2 externally, exchanging HEPES and bicarbonate buffers, and changing pHi with NH4Cl washout. We conclude that in situ confocal fluorescent microscopy can measure pHi and pHo changes at the endocardial surface and deeper endocardial layers in arterially perfused ventricular myocardium. This method has the potential to study pHi regulation in perfused myocardium at boundaries where diffusion of gases, metabolites, and peptides are expected to modify processes that regulate pHi.
Vasopressin contributes to dynorphin modulation of hypoxic cerebrovasodilation
Authors: Venteicher Andrew , Armstead William M.
Published: December 2017

Because pial artery dilation during a 20- or 40-min hypoxic exposure was less than that observed during a 5- or 10-min exposure, stimulus duration determines the vascular response to hypoxia. Dynorphin (Dyn) modulates hypoxic pial dilation and contributes to decremented dilation during longer hypoxic exposures. This study was designed to determine whether vasopressin (VP) contributes to Dyn modulation of hypoxic pial dilation in newborn pigs equipped with a closed cranial window. Moderate (M) and severe (S) hypoxia (arterial [Formula: see text] ∼ 35 and 25 mmHg, respectively) had no effect on cerebrospinal fluid VP during a 5-min exposure but increased its concentration during longer exposure periods. The VP antagonist [β-mercapto-β,β-cyclopentamethylenepropionyl1, O-Me-Tyr2,Arg8]vasopressin (MEAVP) had no influence on pial dilation during the 5-min exposure but potentiated the 20- and 40-min M and S hypoxic exposure dilations: 21 ± 2 vs. 29 ± 3% and 23 ± 2 vs. 33 ± 2% for 20- and 40-min S hypoxic dilation before and after MEAVP. Topical VP during 5 min of hypoxia elicited dilation that was reversed to vasoconstriction during 20 min of S and 40 min of M and S hypoxia. Similarly, during 5 min of hypoxia, Dyn elicited dilation that was reversed to vasoconstriction during longer hypoxic periods. MEAVP blunted this Dyn-induced vasoconstriction. These data show that VP modulates hypoxic pial dilation in a stimulus duration-dependent manner and that VP contributes to the reversal of Dyn from a dilator to a constrictor during prolonged hypoxia. Finally, these data suggest that VP contributes to Dyn modulation of hypoxic cerebrovasodilation.
Leakage responses to l-NAME differ with the fluorescent dye used to label albumin
Authors: Rumbaut Rolando E. , Harris Norman R. , Sial Arshad J. , Huxley Virginia H. , Granger D. Neil
Published: December 2017

Nitric oxide synthase (NOS) inhibitors have been reported to increase as well as to decrease microvascular transport of macromolecules in a variety of models. This study was performed to determine whether the influence of NOS inhibition on albumin leakage was dependent on the fluorescent dyes used to label albumin. Albumin leakage was assessed in rat mesenteric venules during control conditions and after exposure to the NOS inhibitor N G-nitro-l-arginine methyl ester (l-NAME). Albumin was labeled with any one of four dyes: FITC, sulforhodamine 101 [Texas Red (TR)], dichlorotriazinyl aminofluorescein (DTAF), or Oregon Green 514 (OG). Superfusion withl-NAME (10−4 M) was accompanied by an increase in leakage of FITC-labeled albumin ( n = 12) but not of albumin labeled with DTAF ( n = 10), TR ( n = 10), or OG ( n = 4). In vessels perfused with both FITC- and TR-labeled albumin ( n = 12), superfusion with l-NAME increased leakage of FITC- but not TR-labeled albumin. In conclusion, albumin leakage responses tol-NAME differ among various fluorescent dyes. Therefore, caution is advised in comparison of albumin leakage results that utilize different fluorescent dyes.
In vivo effects of hydrostatic pressure on interstitium of abdominal wall muscle
Authors: Zakaria El Rasheid , Lofthouse Joanne , Flessner Michael F.
Published: December 2017

Fluid loss from the peritoneal cavity to surrounding tissue varies directly with intraperitoneal hydrostatic pressure (Pip). According to Darcy’s law [ Q = − KA(dPif/d x)], fluid flux ( Q) across a cross-sectional area ( A) of tissue will increase with an increase in either hydraulic conductivity ( K) or the interstitial fluid hydrostatic pressure gradient (dPif/d x, where x is distance). Previously, we demonstrated that in the anterior abdominal muscle (AAM) of rats, dPif/d xincreases by only 40%, whereas Krises fivefold between Pipof 1.5 and 8 mmHg. Because K is a function of interstitial volume (θif), we hypothesized that perturbations of Pipwould change Pifand expand the interstitium, increasing θif. To test this hypothesis, we used dual-label quantitative autoradiography (QAR) to measure extracellular fluid volume (θec) and intravascular volume (θiv) in the AAM of rats within the Piprange from −2.8 to +8 mmHg. θifwas obtained by subtraction (θec− θiv). dPif/d xwas measured with a micropipette and a servo-null system. Local θivdid not vary with Pipand averaged 0.010 ± 0.002 ml/g, and θifaveraged 0.19 ± 0.01 ml/g at Pif≤1.2 mmHg. However, θifdoubled between Pifof 1.2 and 4.2 mmHg (from 0.20 ± 0.00 to 0.39 ± 0.01 ml/g, respectively) but did not increase with further increases in Pif. This nonlinear pressure-volume relationship does not explain the fivefold increase in K with Pip. Because the interstitial matrix contributes to the interstitial resistance to fluid flow, and because hyaluronan (HA) is the only component of the matrix that is not anchored to the tissue, we hypothesized that the loss of interstitial HA was responsible for the continued decrease in interstitial resistance to fluid flow. We determined HA concentration in the rat AAM and adjacent subcutaneous tissue (SC) at Pip= 0 mmHg and after 2 h of dialysis at constant Pip= 6 mmHg. The HA content (normalized to dry weight) in the AAM was reduced from 487 ± 16 to 360 ± 27 μg/g dry tissue ( n = 4, P < 0.05) and increased from 528 ± 72 to 1,050 ± 136 mg/g dry tissue ( n = 4, P > 0.001) in the SC. We conclude that the mechanisms responsible for the increase in K with Pipinclude expansion of the interstitium, dilution of interstitial macromolecules, and washout from the AAM to SC of interstitial macromolecules responsible for resistance to fluid flow.
Microvascular responses to hemodilution with Hb vesicles as red blood cell substitutes: influence of O2affinity
Authors: Sakai Hiromi , Tsai Amy G. , Rohlfs Ronald J. , Hara Hiroyuki , Takeoka Shinji , Tsuchida Eishun , Intaglietta Marcos
Published: December 2017

Phospholipid vesicles encapsulating purified hemoglobin (HbV) were developed to provide O2-carrying capacity to plasma expanders. Microvascular perfusion was determined for HbV with different O2affinity (P50= 9, 16, and 30 mmHg) prepared by coencapsulating pyridoxal 5′-phosphate (PLP) at the molar ratios of [PLP]/[Hb] = 0, 0.5, and 3, respectively (cf. hamster blood, P50: 28 mmHg), and suspended in 8 g/dl human serum albumin (HSA). Eighty percent of the red blood cell (RBC) mass of conscious Syrian golden hamsters fitted with dorsal skinfold windows was substituted with either of the HbV-HSA suspensions, washed hamster RBC suspended in HSA (RBC-HSA), and HSA alone. All three HbV-HSA groups and RBC-HSA groups showed stable blood pressure and heart rate, which could not be sustained with HSA alone. Only the HbV (P50= 9)-HSA group showed an increase in arterial O2tension (89.8 ± 14.7 mmHg, baseline 58.4 ± 4.0 mmHg) because of hyperventilation, and microvascular perfusion was decreased, indicating that facilitated O2unloading of HbV by decreasing the O2affinity (increasing P50) with PLP as an allosteric effector is important. Microvascular perfusion and microvascular and interstitial O2tensions in the HbV (P50= 16 and 30)-HSA groups were significantly higher than those in the HSA group. The O2release rate from the HbV was 18–32 s−1vs. 4.4 s−1for RBC. Functional capillary density was improved from 17 to 41% on average by decreasing P50from 30 to 16 mmHg, which appears to be an optimal value for the P50in this system.
Inhibition of copper/zinc superoxide dismutase impairs NO ⋅-mediated endothelium-dependent relaxations
Authors: Wambi-Kiéssé Christel O. , Katusic Zvonimir S.
Published: December 2017

The superoxide anion ([Formula: see text]) appears to be an important modulator of nitric oxide (NO ⋅) bioavailability. The present study was designed to characterize the role of copper/zinc superoxide dismutase (Cu/Zn SOD) in endothelium-dependent relaxations. Cu/Zn SOD was inhibited with the Cu2+chelator diethyldithiocarbamic acid (DETCA). In isolated canine basilar arteries, DETCA (7.6 × 10−3M) inhibited total vascular SOD activity by 46% ( P < 0.0001, n = 6–8 dogs). DETCA (7.6 × 10−3M) significantly reduced relaxations to bradykinin and A-23187 ( P < 0.05, n = 7–11). The inhibitory effect of DETCA was abolished by the [Formula: see text]scavenger 4,5-dihydroxy-1,3-benzenedisulfonic acid (Tiron; 9.4 × 10−3M; P < 0.05, n = 6–13). Tiron significantly potentiated the relaxations to bradykinin in control rings ( P < 0.05, n = 13), and the nitric oxide synthase inhibitor Nω-nitro-l-arginine methyl ester (l-NAME; 3 × 10−4M) abolished these relaxations ( P < 0.0001, n = 6). DETCA and Tiron had no effect on the relaxations to diethylamine-NONOate or forskolin ( P > 0.05, n = 6). Our results demonstrate that endothelium-dependent relaxations mediated by NO ⋅ are impaired after the inhibition of Cu/Zn SOD. Relaxations to bradykinin (but not A-23187) were significantly augmented by Tiron. Pharmacological scavenging of [Formula: see text]reverses the effect of Cu/Zn SOD inhibition.
Hypotension induced by exercise is associated with enhanced release of adenyl purines from aged rat artery
Authors: Hashimoto M. , Shinozuka K. , Tanabe Y. , Gamoh S. , Hara T. , Hossain M. S. , Kwon Y. M. , Kunitomo M. , Masumura S.
Published: December 2017

To determine whether the antihypertensive effects of exercise are associated with release of ATP and its metabolites from arteries, we assayed blood pressure and the release of adenine nucleotides and nucleosides from the caudal arteries of exercised and sedentary aged hypercholesterolemic rats. Exercise on a treadmill for 12 wk significantly decreased the rise in systolic and diastolic blood pressure by 7.5 and 15.9%, respectively, with advanced age. The concentrations of oleic, linoleic, and linolenic acids in the caudal artery decreased significantly with exercise, demonstrating an association between exercise and the unsaturation index of caudal arterial fatty acids. The amounts of total adenyl purines released by the arterial segments from exercised rats, both spontaneously and in response to norepinephrine, were significantly greater by 80.0 and 60.7%, respectively, than those released by tissues from sedentary rats. These results suggest that exercise alters the membrane fatty acid composition in aged rats as well as the release of ATP from vascular endothelial cells and that these factors are associated with the regression of the rise in blood pressure normally observed with advanced age.
Metallothionein inhibits ischemia-reperfusion injury in mouse heart
Authors: Kang Y. James , Li Guangqiu , Saari Jack T.
Published: December 2017

Oxidative stress is believed to play a major role in ischemia-reperfusion injury to the heart. Metallothionein (MT), a potential free radical scavenger, may function in cardiac protection against ischemia-reperfusion damage. To test this hypothesis, a specific cardiac MT-overexpressing transgenic mouse model was used. The hearts isolated from these animals were subjected to 50 min of warm (37°C) zero-flow ischemia followed by 60- or 90-min reflow. Compared with the nontransgenic controls, the transgenic mouse hearts with MT concentrations ∼10-fold higher than normal showed significantly improved recovery of contractile force postischemia (69.2 ± 4.2 vs. 26.0 ± 6.0% at the end of 60-min reperfusion, P < 0.01). Efflux of creatine kinase from these transgenic hearts was reduced by more than 50% ( P < 0.01). In addition, the zone of infarction induced by ischemia-reperfusion at the end of 90-min reperfusion was suppressed by ∼40% ( P < 0.01) in the transgenic hearts. The results strongly indicate that MT provides protection against ischemia-reperfusion-induced heart injury.
Ischemic preconditioning depends on interaction between mitochondrial KATPchannels and actin cytoskeleton
Authors: Baines Christopher P. , Liu Guang S. , Birincioglu Mustafa , Critz Stuart D. , Cohen Michael V. , Downey James M.
Published: December 2017

Both mitochondrial ATP-sensitive K+(KATP) channels and the actin cytoskeleton have been proposed to be end-effectors in ischemic preconditioning (PC). For evaluation of the participation of these proposed end effectors, rabbits underwent 30 min of regional ischemia and 3 h of reperfusion. PC by 5-min ischemia + 10-min reperfusion reduced infarct size by 60%. Diazoxide, a mitochondrial KATP-channel opener, administered before ischemia was protective. Protection was lost when diazoxide was given after onset of ischemia. Anisomycin, a p38/JNK activator, reduced infarct size, but protection from both diazoxide and anisomycin was abolished by 5-hydroxydecanoate (5-HD), an inhibitor of mitochondrial KATPchannels. Isolated adult rabbit cardiomyocytes were subjected to simulated ischemia by centrifuging the cells into an oxygen-free pellet for 3 h. PC was induced by prior pelleting for 10 min followed by resuspension for 15 min. Osmotic fragility was assessed by adding cells to hypotonic (85 mosmol) Trypan blue. PC delayed the progressive increase in fragility seen in non-PC cells. Incubation with diazoxide or pinacidil was as protective as PC. Anisomycin reduced osmotic fragility, and this was reversed by 5-HD. Interestingly, protection by PC, diazoxide, and pinacidil could be abolished by disruption of the cytoskeleton by cytochalasin D. These data support a role for both mitochondrial KATPchannels and cytoskeletal actin in protection by PC.
Wortmannin inhibits insulin-stimulated activation of protein phosphatase 1 in rat cardiomyocytes
Authors: de Luca Jane P. , Garnache Alice K. , Rulfs Jill , Miller Thomas B.
Published: December 2017

A major function of insulin in target tissues is the activation of glycogen synthase. Phosphatidylinositol 3-kinase (PI3K) has been implicated in the insulin-induced activation of glycogen synthase, although the true function of this enzyme remains unclear. Data presented here demonstrate that the PI3K inhibitors wortmannin and LY-294002 block the insulin-stimulated activation of protein phosphatase 1 (PP1) in rat ventricular cardiomyocytes. This loss of phosphatase activation mimics that seen in diabetic cardiomyocytes, in which insulin stimulation fails to activate both PP1 and glycogen synthase. Interestingly, in diabetic cells, insulin stimulated PI3K activity to 300% of that in untreated controls, whereas this activity was increased by only 77% in normal cells. PI3K protein levels, however, were similar in normal and diabetic cells. Our results indicate that PI3K is involved in the stimulation of glycogen synthase activity by insulin through the regulation of PP1. The inability of insulin to stimulate phosphatase activity in diabetic cells, despite a significant increase in PI3K activity, suggests a defect in the insulin signaling pathway that contributes to the pathology of insulin-dependent diabetes.
Activation of spinal opioid receptors contributes to hypotension after hemorrhage in conscious rats
Authors: Ang Kooi K. , McRitchie Robert J. , Minson Jane B. , Llewellyn-Smith Ida J. , Pilowsky Paul M. , Chalmers John P. , Arnolda Leonard F.
Published: December 2017

Opioid receptors are activated during severe hemorrhage, resulting in sympathoinhibition and a profound fall in blood pressure. This study examined the location and subtypes of opioid receptors that might contribute to hypotension after hemorrhage. Intrathecal naloxone methiodide (100 nmol) abolished the fall in blood pressure after hemorrhage (1.5% of body wt; mean arterial pressure 122 ± 8 mmHg after naloxone methiodide vs. 46 ± 5 mmHg in controls, P < 0.001). Intracisternal naloxone methiodide was less effective than intrathecal naloxone methiodide, whereas intravenous naloxone methiodide, which does not cross the blood-brain barrier, did not alter the fall in blood pressure after hemorrhage. These results demonstrate that spinal opioid receptors contribute to hypotension after hemorrhage but do not exclude supraspinal effects. In separate experiments, the subtype-specific opioid antagonists ICI-174864 (δ-antagonist), norbinaltorphimine (nor-BNI; κ-antagonist), and H-d-Phe-Cys-Tyr-d-Trp-Orn-Thr-Pen-Thr-NH2(CTOP; μ-antagonist) were each administered intrathecally to determine the minimum dose that would attenuate hypotension during severe hemorrhage. These antagonists were effective at similar doses (3 nmol for CTOP, 6 nmol for ICI-174864, and 10 nmol for nor-BNI), although the binding affinities of these three different agents for their target receptors varied >1600-fold. Comparisons of the minimum effective doses of these antagonists in relation to their binding affinities provides strong evidence for the participation of δ-receptors in mediating hypotension after hemorrhage. In contrast, the dose at which nor-BNI was effective suggests an effect at δ-receptors but not κ-receptors. The efficacy of CTOP, albeit at a high dose, also suggests an effect at μ-receptors.
Ser16prevails over Thr17phospholamban phosphorylation in the β-adrenergic regulation of cardiac relaxation
Authors: Kuschel Meike , Karczewski Peter , Hempel Petra , Schlegel Wolfgang-Peter , Krause Ernst-Georg , Bartel Sabine
Published: December 2017

Phospholamban is a critical regulator of sarcoplasmic reticulum Ca2+-ATPase and myocardial contractility. To determine the extent of cross signaling between Ca2+and cAMP pathways, we have investigated the β-adrenergic-induced phosphorylation of Ser16and Thr17of phospholamban in perfused rat hearts using antibodies recognizing phospholamban phosphorylated at either position. Isoproterenol caused the dose-dependent phosphorylation of Ser16and Thr17with strikingly different half-maximal values (EC50= 4.5 ± 1.6 and 28.2 ± 1.4 nmol/l, respectively). The phosphorylation of Ser16induced by isoproterenol, forskolin, or 3-isobutyl-1-methylxanthine correlated to increased cardiac relaxation ( r = 0.96), whereas phosphorylation of Thr17did not. Elevation of extracellular Ca2+did not induce phosphorylation at Thr17; only in the presence of a submaximal dose of isoproterenol, phosphorylation at Thr17increased eightfold without additional effects on relaxation rate. Thr17phosphorylation was partially affected by ryanodine and was completely abolished in the presence of 1 μmol/l verapamil or nifedipine. The data indicate that 1) phosphorylation of phospholamban at Ser16by cAMP-dependent protein kinase is the main regulator of β-adrenergic-induced cardiac relaxation definitely preceding Thr17phosphorylation and 2) the β-adrenergic-mediated phosphorylation of Thr17by Ca2+-calmodulin-dependent protein kinase required influx of Ca2+through the L-type Ca2+channel.
Characterization of natriuretic peptide production by adult heart atria
Authors: Ogawa Tsuneo , Vatta Marcelo , Bruneau Benoit G. , de Bold Adolfo J.
Published: December 2017

The cardiac polypeptide hormones atrial natriuretic factor (ANF) and brain natriuretic peptide (BNP) are synthesized and costored by atrial cardiocytes and share receptors and many biologic properties. Although some aspects of their synthesis and release are specific for each peptide, it is not clear whether they share intracellular sorting and secretory mechanisms. In the present work we take advantage of a stable isolated rat atrial preparation that allows, for the first time, long-term study of synthesis, trafficking, targeting, and secretion of ANF and BNP by adult atrial muscle. Three model stimuli of secretion were used: increased intra-atrial pressure, endothelin-1 (ET-1), and phenylephrine (PE), representing mechanical, hormonal, and α1-adrenergic stimuli, respectively. To gain further insight into the secretory process under basal and agonist-induced secretion, we employed agents known to inhibit protein synthesis (cycloheximide) or to interfere with the vectorial transport of protein targeted for secretion (brefeldin A and monensin). All these agents induced significant changes in ANF and BNP release. Cycloheximide decreased natriuretic peptide secretion under basal and stimulated conditions. Brefeldin A dramatically increased basal as well as stimulated secretion of ANF and BNP. Monensin partially decreased basal ANF and BNP secretion and completely blocked stimulated secretion. None of these agents modified proteolytic processing as assessed by reverse-phase HPLC analysis. Double-label pulse-chase experiments using [3H]- and [14C]leucine demonstrated that the secretory response to ET-1, in contrast to the response to muscle stretch, is based on peptide other than newly synthesized or relatively newly stored ANF. It is concluded that, in adult atrial cardiocytes, ANF and BNP are sorted to constitutive and regulated pathways in a manner that is substantially unique for atrial cardiocytes. In particular, it appears that basal and stimulated ANF and BNP secretion may have a large “constitutive-like” component, as previously defined in other endocrine systems. This type of secretion is based on the preferential release of hormone through vesicles arising from immature secretory granules. The capacity of the atria to release ANF and BNP in response to stimuli, therefore, may depend more on stimulation of the rate of formation of immature granules than on the amount of stored hormone.
Reduced coronary NO production in conscious dogs after the development of alloxan-induced diabetes
Authors: Zhao Gong , Zhang Xiaoping , Smith Carolyn J. , Xu Xiaobin , Ochoa Manuel , Greenhouse David , Vogel Traci , Curran Christine , Hintze Thomas H.
Published: December 2017

The role of nitric oxide (NO) in the control of coronary blood flow (CBF) during the development of diabetes is unknown. To study this, mongrel dogs were chronically instrumented using sterile techniques for measurements of systemic hemodynamics and CBF. With heart rate controlled (150 beats/min), veratrine (1–10 μg/kg) caused dose-dependent increases in CBF; e.g., 5 μg/kg of veratrine increased CBF by 57 ± 7% from 41 ± 1.3 ml/min ( P < 0.05). The dogs developed diabetes 4–5 wk after injection of alloxan (40–60 mg/kg iv, blood glucose levels were 384 ± 18 mg/dl). After diabetes the same doses of veratrine caused smaller increases in CBF; i.e., 5 μg/kg of veratrine increased CBF by 32 ± 2% ( P < 0.05 compared with control) from 28 ± 4 ml/min. ACh- and adenosine-induced coronary vasodilation were reduced after diabetes as well. In anesthetized dogs after diabetes, vagal stimulation caused smaller increases in CBF. ACh and bradykinin caused smaller increases in[Formula: see text] production in coronary microvessels from diabetic dogs. Furthermore, despite the fact that mRNA for endothelial cell NO synthase from the aorta was increased twofold with the use of Northern blotting, the protein for aortic endothelial constitutive NO synthase was reduced by 66% after diabetes, as determined by Western blotting. Our results indicate that the NO-dependent coronary vasodilation by the Bezold-Jarisch reflex is impaired in conscious dogs after diabetes. The mechanism responsible for the impaired endothelium-dependent coronary vasodilation is most likely the decreased release of NO from the endothelium.
pH regulation of K+efflux from myocytes in isolated rat hearts:87Rb,7Li, and31P NMR studies
Authors: Kupriyanov V. V. , Xiang B. , Kuzio B. , Deslauriers R.
Published: December 2017

This study investigates the effects of intracellular (pHi) and extracellular pH (pHe) on the efflux of Rb+and Li+in isolated rat hearts.87Rb and7Li NMR were used to measure Rb+and Li+content, respectively, of hearts, and31P NMR was used to monitor pHi, pHe, and phosphate levels. After 30-min equilibration with Rb+or Li+, effluxes were initiated by switching perfusion to a Rb+- or Li+-free, high-K+(20.7 mM) Krebs-Henseleit buffer with 15 μM bumetanide. Monensin (2 μM) increased pHifrom 7.10 ± 0.05 to 7.32 ± 0.07 and resulted in activation of Rb+efflux; the first-order rate constant ( k × 103, in min−1) increased from 42 ± 2 to 116 ± 16. Glibenclamide (4 μM) did not inhibit monensin-activated Rb+efflux ( k = 110 ± 17), whereas quinine (0.2 mM) slightly inhibited it by 19 ± 9%. Infusion of 15 mM NH4Cl during Rb+washout increased k for Rb+efflux by 93% (81 ± 8), which was glibenclamide and quinine insensitive, and caused a transient increase in pHito 7.25 ± 0.08. Intracellular Li+inhibited NH4Cl-stimulated Rb+efflux by 55%. Monensin and NH4Cl stimulated Li+efflux by 40%, increasing k from 29 ± 3 to 43 ± 7 and 41 ± 3, respectively. The stimulation was not sensitive to 10 μM dimethylamiloride. Intracellular acidosis that resulted from the washout of NH4Cl (pH 6.86 ± 0.2) slightly inhibited Rb+efflux ( k = 36 ± 5), whereas NH4Cl itself in the absence of pHichanges did not markedly affect Rb+efflux. A moderate increase in pHi(7.17 ± 0.06) produced by washout of 15 mM 2,2-dimethylpropionate (DMP)-Tris from hearts preequilibrated with DMP did not markedly affect Rb+efflux. Neither global alkalosis (pHi7.4, pHe7.55) nor acidosis (pHi≈ pHe6.8) produced by 3 mM Tris base or 5 mM MES, respectively, affected Rb+efflux. We suggest that intracellular alkalosis stimulates Rb+(K+) and Li+effluxes by activating a nonselective sarcolemmal K+(Li+)/cation exchanger or a K+(Li+)-anion symporter.
Interaction of angiotensin II and the insulin-like growth factor system in vascular smooth muscle cells
Authors: Gustafsson Thomas , Andersson Peter , Chen Yun , Magnusson Jan Olof , Arnqvist Hans J.
Published: December 2017

We studied the effects and interactions of ANG II and the insulin-like growth factor (IGF) system in cultured rat aortic smooth muscle cells. ANG II (1 μM) and IGF-I (10 nM) stimulated both DNA and protein synthesis. The effects of the two peptides in combination were additive or more than additive. The AT1receptor antagonist losartan (10 and 100 μM) blocked their synergistic effect on DNA synthesis. IGF binding protein (IGFBP)-1 inhibited the effect of IGF-I but not that of ANG II on DNA synthesis. IGF-I stimulated gene expression of IGFBP-2 and IGFBP-4. ANG II decreased IGF-I, IGFBP-2, and IGFBP-4 transcripts but increased the IGF-I receptor transcript. IGF-I and ANG II in combination had similar effects on gene expression as ANG II alone. The IGFBP-2 and IGFBP-4 peptides could be detected in the conditioned medium. Our results show that ANG II and IGF-I have synergistic effects on vascular smooth muscle cells and that they interact in several ways.
Myocardial tumor necrosis factor-α secretion in hypertensive and heart failure-prone rats
Authors: Bergman Marina R. , Kao Ruey H. , McCune Sylvia A. , Holycross Bethany J.
Published: December 2017

Acute increases in blood pressure (BP) increase myocardial tumor necrosis factor (TNF)-α production, but it is not known whether chronic hypertensive stress elevates myocardial TNF-α production, possibly contributing to cardiac remodeling, decreased cardiac function, and faster progression to heart failure. BP, cardiac function, and size were evaluated in normotensive [Sprague-Dawley (SD)], spontaneously hypertensive (SHR), and spontaneously hypertensive heart failure-prone (SHHF) rats at 6, 12, 15, and 18 mo of age and in failing SHHF. Left ventricular tissues were evaluated for secretion of bioactive TNF-α and inhibition of TNF-α secretion by phosphodiesterase inhibitors. All ventricles secreted bioactive and immunoreactive TNF-α, but secretion decreased with age. SHR and SHHF rats secreted more TNF-α than SD rats at 6 mo of age, but only failing SHHF rats secreted significantly more TNF-α at 18 mo. Amrinone inhibited TNF-α secretion in all rats and was less potent but more efficacious than RO-201724 in all strains. TNF-α secretion correlated with BP and left ventricular mass in 6-mo-old rats, but this relationship disappeared with age. Results suggest that hypertension and/or cardiac remodeling is associated with elevated myocardial TNF-α, and, although hypertension, per se, did not maintain elevated cardiac TNF-α levels, SHHF rats increase TNF-α production during the end stages of failure.