bluuebunny/crossref_metadata_2025 huggingface dataset:
Inhaled NO reduces leukocyte-endothelial cell interactions and myocardial dysfunction in endotoxemic rats
Authors: Nevière Rémi , Guery Benoit , Mordon Serge , Zerimech Farid , Charré Stéphane , Wattel Francis , Chopin Claude
Published: December 2017

Inhaled nitric oxide (NO) has been shown to have some protective effect in the peripheral distal inflamed vasculature. The objective of the study was to determine whether inhaled NO would reduce endotoxin-induced leukocyte activation and myocardial contractile dysfunction. Rats were treated with either saline or endotoxin (10 mg/kg iv) and then allowed to breathe (4 h) either air or air plus NO (10 ppm). In endotoxemic rats, mesenteric venular endothelium leukocyte firm adhesion increased compared with control rats (1.15 ± 0.32 vs. 4.08 ± 0.96 leukocytes/100 μm; P < 0.05). Inhaled NO significantly attenuated endotoxin-induced venular endothelium leukocyte adhesion (4.08 ± 0.96 vs. 1.86 ± 0.76 leukocytes/100 μm; P < 0.05) and FITC-conjugated anti-intercellular adhesion molecule-1 fluorescence intensity. Endotoxin-induced myocardial dysfunction and leukocyte content increases were reduced in inhaled NO-treated rats. These observations suggest that inhaled NO reduces the degree of cardiovascular dysfunction and inflammation in endotoxemic rats.
Impaired nitric oxide-mediated vasodilation in transgenic sickle mouse
Authors: Kaul Dhananjaya K. , Liu Xiao-Du , Fabry Mary E. , Nagel Ronald L.
Published: December 2017

Transgenic sickle mice expressing human βS- and βS-Antilles-globins show intravascular sickling, red blood cell adhesion, and attenuated arteriolar constriction in response to oxygen. We hypothesize that these abnormalities and the likely endothelial damage, also reported in sickle cell anemia, alter nitric oxide (NO)-mediated microvascular responses and hemodynamics in this mouse model. Transgenic mice showed a lower mean arterial pressure (MAP) compared with control groups (90 ± 7 vs. 113 ± 8 mmHg, P < 0.00001), accompanied by increased endothelial nitric oxide synthase (eNOS) expression. NG-nitro-l-arginine methyl ester (l-NAME), a nonselective inhibitor of NOS, caused an ∼30% increase in MAP and ∼40% decrease in the diameters of cremaster muscle arterioles (branching orders: A2 and A3) in both control and transgenic mice, confirming NOS activity; these changes were reversible after l-arginine administration. Aminoguanidine, an inhibitor of inducible NOS, had no effect. Transgenic mice showed a decreased ( P < 0.02–0.01) arteriolar dilation in response to NO-mediated vasodilators, i.e., ACh and sodium nitroprusside (SNP). Indomethacin did not alter the responses to ACh and SNP. Forskolin, a cAMP-activating agent, caused a comparable dilation of A2 and A3 vessels (∼44 and 70%) in both groups of mice. Thus in transgenic mice, an increased eNOS/NO activity results in lower blood pressure and diminished arteriolar responses to NO-mediated vasodilators. Although the increased NOS/NO activity may compensate for flow abnormalities, it may also cause pathophysiological alterations in vascular tone.
Somatostatin receptor subtype expression and function in human vascular tissue
Authors: Curtis Susan B. , Hewitt Jeff , Yakubovitz Svetlana , Anzarut Alexander , Hsiang York N. , Buchan Alison M. J.
Published: December 2017

In animal models the somatostatin analog angiopeptin inhibits intimal hyperplasia by acting primarily through somatostatin receptor 2 (SSTR-2). However, the results of clinical trials using angiopeptin have been disappointing. In this study we showed that human blood vessels express high levels of SSTR-1 with significantly lower levels of SSTR-2 and -4. Samples of normal veins and arteries, as well as atherosclerotic arteries, expressed predominantly SSTR-1. In addition, the levels of SSTR-1 varied between individuals, indicating that the vascular disease process may have affected SSTR gene expression. Immunocytochemical studies demonstrated that SSTR-1 was present in endothelial but not vascular smooth muscle cells. No evidence of SSTR-3 or -5 expression was detected in normal or diseased blood vessels. Two endothelial cell preparations, ECV304 and human umbilical vein endothelial cells, were investigated and shown to express only SSTR-1 and -4. Exposure of these cells to 10 nM somatostatin or 10 nM SSTR-1-specific agonist resulted in alterations to the actin cytoskeleton, as characterized by a loss of actin stress fibers coupled with an increase in lamellipodia formation at the plasma membrane. These results suggest that the lack of effectiveness of angiopeptin in humans may be due to the differential expression of SSTR-1 by human endothelial cells.
Selective plasmalogen substrate utilization by thrombin-stimulated Ca2+-independent PLA2in cardiomyocytes
Authors: McHowat Jane , Creer Michael H.
Published: December 2017

Thrombin stimulation of rabbit ventricular myocytes activates a membrane-associated, Ca2+-independent phospholipase A2(PLA2) capable of hydrolyzing plasmenylcholine (choline plasmalogen), plasmanylcholine (alkylacyl choline phospholipid), and phosphatidylcholine substrates. To identify the endogenous phospholipid substrates, we quantified the effects of thrombin stimulation on diradyl phospholipid mass and arachidonic acid and lysophospholipid production. Thrombin stimulation resulted in a selective decrease in arachidonylated plasmenylcholine, with no change in arachidonylated phosphatidylcholine. The decrease in arachidonylated plasmenylcholine was accompanied by an increase in plasmenylcholine species containing linoleic and linolenic acids at the sn-2 position. A decrease in arachidonylated plasmenylethanolamine was also observed after thrombin stimulation, with no concomitant change in arachidonylated phosphatidylethanolamine. Thrombin stimulation resulted in the selective production of lysoplasmenylcholine, with no increase in lysophosphatidylcholine content. There was no evidence for significant acetylation of lysophospholipids to form platelet-activating factor. Arachidonic acid released after thrombin stimulation was rapidly oxidized to prostacyclin. Thus thrombin-stimulated Ca2+-independent PLA2selectively hydrolyzes arachidonylated plasmalogen substrates, resulting in production of lysoplasmalogens and prostacyclin as the principal bioactive products.
Potassium channels modulate cerebral autoregulation during acute hypertension
Authors: Paternò Roberto , Heistad Donald D. , Faraci Frank M. ,   (With the Technical Assistance of Dale Kinzenbaw)
Published: December 2017

We tested the hypothesis that constriction of cerebral arterioles during acute increases in blood pressure is attenuated by activation of potassium (K+) channels. We tested the effects of inhibitors of calcium-dependent K+ channels [iberiotoxin (50 nM) and tetraethylammonium (TEA, 1 mM)] on changes in arteriolar diameter during acute hypertension. Diameter of cerebral arterioles (baseline diameter = 46 ± 2 μm, mean ± SE) was measured using a cranial window in anesthetized rats. Arterial pressure was increased from a control value of 96 ± 1 mmHg to 130, 150, 170, and 200 mmHg by intravenous infusion of phenylephrine. Increases in arterial pressure from baseline to 130 and 150 mmHg decreased the diameter of cerebral arterioles by 5–10%. Greater increases in arterial pressure produced large increases in arteriolar diameter (i.e., “breakthrough of autoregulation”). Iberiotoxin or TEA inhibited increases in arteriolar diameter when arterial pressure was increased to 170 and 200 mmHg. The change in arteriolar diameter at 200 mmHg was 20 ± 3% and −1 ± 4% in the absence and presence of iberiotoxin, respectively. These findings suggest that calcium-dependent K+ channels attenuate cerebral microvascular constriction during acute increases in arterial pressure, and that increases in arteriolar diameter at high levels of arterial pressure are not simply a passive phenomenon.
Sulfonylurea receptor ligands modulate stretch-induced ANF secretion in rat atrial myocyte culture
Authors: Jiao Jin-Hua , Baumann Philippe , Baron Anne , Roatti Angela , Pence Richard A. , Baertschi Alex J.
Published: December 2017

Stretch-induced atrial natriuretic factor (ANF) secretion was studied in cultures of neonate atrial appendage myocytes. Stretch, applied for 40 min by hypotonic swelling, increased the mean area of 44 individually imaged myocytes by 4.8–8.8% ( P < 0.0001) at 6 min and by 2.3–6.2% ( P < 0.05) at 35 min. Stretch increased immunoreactive ANF release by 42% ( P < 0.05) from a baseline of 315 pg/ml. The ATP-sensitive K+(KATP)-channel blocker tolbutamide (100 μmol/l) increased the stretch-stimulated release to 84% ( P < 0.01) over baseline, whereas lower concentrations (1, 10, and 30 μmol/l) had no stimulatory effect. The KATP-channel opener diazoxide (0.1, 1, 10, 30, and 100 μmol/l) inhibited stretch- plus tolbutamide-stimulated ANF release in a concentration-dependent manner, with IC50 = 2.2 μmol/l, although 100 μmol/l diazoxide did not reduce the increase in mean cell area. The stretch-stimulated KATP current, monitored in 82 whole cell recordings with sulfonylurea receptor (SUR) ligands, was inversely correlated with the stretch-induced ANF release ( r 2 = 0.79, P < 0.0001). In the absence of stretch, the KATP current had no relationship with baseline ANF release, and baseline ANF release was not affected by the KATP-channel modulators. The results show that SUR ligands that open KATP channels inhibit stretch-induced ANF release in atrial myocytes, in correlation with the stretch-activated KATP current. The subcellular site of action of the SUR ligands—plasmalemma or intracellular organelles—remains to be determined.
Differential role of ionotropic glutamatergic mechanisms in responses to NTS P2x and A2a receptor stimulation
Authors: Scislo Tadeusz J. , O'Leary Donal S.
Published: December 2017

Activation of ATP P2x receptors in the subpostremal nucleus tractus solitarii (NTS) via microinjection of α,β-methylene ATP (α,β-MeATP) elicits fast initial depressor and sympathoinhibitory responses that are followed by slow, long-lasting inhibitory effects. Activation of NTS adenosine A2a receptors via microinjection of CGS-21680 elicits slow, long-lasting decreases in arterial pressure and renal sympathetic nerve activity (RSNA) and an increase in preganglionic adrenal sympathetic nerve activity (pre-ASNA). Both P2x and A2a receptors may operate via modulation of glutamate release from central neurons. We investigated whether intact glutamatergic transmission is necessary to mediate the responses to NTS P2x and A2areceptor stimulation. The hemodynamic and neural (RSNA and pre-ASNA) responses to microinjections of α,β-MeATP (25 pmol/50 nl) and CGS-21680 (20 pmol/50 nl) were compared before and after pretreatment with kynurenate sodium (KYN; 4.4 nmol/100 nl) in chloralose-urethan-anesthetized male Sprague-Dawley rats. KYN virtually abolished the fast responses to α,β-MeATP and tended to enhance the slow component of the neural responses. The depressor responses to CGS-21680 were mostly preserved after pretreatment with KYN, although the increase in pre-ASNA was reduced by one-half following the glutamatergic blockade. We conclude that the fast responses to stimulation of NTS P2x receptors are mediated via glutamatergic ionotropic mechanisms, whereas the slow responses to stimulation of NTS P2x and A2a receptors are mediated mostly via other neuromodulatory mechanisms.
Phosphorylation at tyrosine-524 influences nuclear accumulation of HSP72 with heat stress
Authors: Knowlton A. A. , Grenier M. , Kirchhoff S. R. , Salfity M.
Published: December 2017

Nuclear accumulation of heat shock protein (HSP) 72 occurs after cardiac ischemia. This nuclear accumulation of HSP72 with stress occurs in other tissues and species. We postulated that nuclear accumulation of HSP72 was important for the protective effect of HSP72 and that phosphorylation of a single tyrosine (Y524) regulated nuclear accumulation of HSP72. Western blots of immunoprecipitated HSP72 from Cos-1 cells demonstrated that tyrosine becomes phosphorylated after heat shock. Treatment with the tyrosine kinase inhibitor geldanamycin blocked nuclear accumulation of HSP72 with heat shock. Two epitope-tagged constructs were made: M17 converting Y524to aspartic acid (pseudophosphorylation) and M18 converting Y524to phenylalanine. When transfected into Cos-1 cells, M17 accumulates more rapidly and M18 less rapidly than wild-type (WT) HSP72 in the nucleus following heat shock. Cells expressing M18 had less viability after heat shock at 43.5°C than other constructs. After heat shock at 45°C, cells expressing M17 had superior survival compared with WT and M18. These data suggest that phosphorylation at Y524facilitates nuclear accumulation of HSP72 following heat stress, and substitution of aspartic acid at Y524enhances resistance to heat-shock injury.
Low [Mg2+]oinduces contraction of cerebral arteries: roles of tyrosine and mitogen-activated protein kinases
Authors: Yang Zhi-Wei , Wang Jun , Zheng Tao , Altura Bella T. , Altura Burton M.
Published: December 2017

The present study was designed to investigate the mechanism of action of low extracellular magnesium ion concentration ([Mg2+]o) on isolated canine basilar arteries and single cerebral vascular smooth muscle cells from these arteries. Low-[Mg2+]omedium (0–0.6 mM) produces endothelium-independent contractions in isolated canine basilar arteries in a concentration-dependent manner; the lower the concentration of [Mg2+]o, the stronger the contractions. The low-[Mg2+]omedium-induced contractions are significantly attenuated by pretreatment of the arteries with low concentrations of either SB-203580, U-0126, PD-98059, genistein, or an Src homology 2 (SH2) domain inhibitor peptide. IC50levels obtained for these five antagonists are consistent with reported inhibitor constant ( Ki) values for these tyrosine kinase and mitogen-activated protein kinase (MAPK) antagonists. Low-[Mg2+]omedium (0–0.6 mM) produces transient intracellular calcium ion concentration ([Ca2+]i) peaks followed by a slow, sustained, and elevated plateau of [Ca2+]iin primary single smooth muscle cells from canine basilar arteries. Low-[Mg2+]omedium induces rapid and stable increases in [Ca2+]i; these increases are inhibited markedly in the presence of either SB-203580, U-0126, PD-98059, genistein or a SH2 domain inhibitor peptide. Several specific antagonists of known endogenously formed vasoconstrictors do not inhibit or attenuate either the low-[Mg2+]o-induced contractions or the elevation of [Ca2+]i. The present study suggests that activation of several cellular signaling pathways, such as protein tyrosine kinases (including the Src family) and MAPK, appears to play important roles in low-[Mg2+]o-induced contractions and the elevation of [Ca2+]iin smooth muscle cells from canine basilar arteries.
Shear stress enhances human endothelial cell wound closure in vitro
Authors: Albuquerque Maria Luiza C. , Waters Christopher M. , Savla Ushma , Schnaper H. William , Flozak Annette S.
Published: December 2017

Repair of the endothelium occurs in the presence of continued blood flow, yet the mechanisms by which shear forces affect endothelial wound closure remain elusive. Therefore, we tested the hypothesis that shear stress enhances endothelial cell wound closure. Human umbilical vein endothelial cells (HUVEC) or human coronary artery endothelial cells (HCAEC) were cultured on type I collagen-coated coverslips. Cell monolayers were sheared for 18 h in a parallel-plate flow chamber at 12 dyn/cm2 to attain cellular alignment and then wounded by scraping with a metal spatula. Subsequently, the monolayers were exposed to a laminar shear stress of 3, 12, or 20 dyn/cm2 under shear-wound-shear (S-W-sH) or shear-wound-static (S-W-sT) conditions for 6 h. Wound closure was measured as a percentage of original wound width. Cell area, centroid-to-centroid distance, and cell velocity were also measured. HUVEC wounds in the S-W-sH group exposed to 3, 12, or 20 dyn/cm2 closed to 21, 39, or 50%, respectively, compared with only 59% in the S-W-sT cells. Similarly, HCAEC wounds closed to 29, 49, or 33% (S-W-sH) compared with 58% in the S-W-sT cells. Cell spreading and migration, but not proliferation, were the major mechanisms accounting for the increases in wound closure rate. These results suggest that physiological levels of shear stress enhance endothelial repair.
Sodium-potassium-ATPase electrogenicity in cerebral precapillary arterioles
Authors: Quinn K. , Guibert C. , Beech D. J.
Published: December 2017

Electrogenicity of the Na+/K+pump has the capability to generate a large negative membrane potential independently of ion-channel current. The high background membrane resistance of arterioles may make them susceptible to such an effect. Pump current was detected by patch-clamp recording from smooth muscle cells in fragments of arterioles (diameter 24–58 μm) isolated from pial membrane of rabbit cerebral cortex. The current was 20 pA at −60 mV, and the extrapolated zero current potential was −160 mV. Two methods of estimating the effect of pump electrogenicity on resting potential indicated an average contribution of −35 mV. In 20% of the recordings, block of inward rectifier K+channels by 10–100 μM Ba2+led to a small depolarization, but hyperpolarization was a more common response. Ba2+also inhibited depolarization evoked by 20 mM K+. In arterioles within intact pial membrane, Ba2+failed to evoke constriction but inhibited K+-induced constriction. The data suggest that cerebral arterioles are vulnerable to the hyperpolarizing effect of the Na+/K+pump, excessive effects of which are prevented by depolarizing inward rectifier K+current
Mathematical models of action potentials in the periphery and center of the rabbit sinoatrial node
Authors: Zhang H. , Holden A. V. , Kodama I. , Honjo H. , Lei M. , Varghese T. , Boyett M. R.
Published: December 2017

Mathematical models of the action potential in the periphery and center of the rabbit sinoatrial (SA) node have been developed on the basis of published experimental data. Simulated action potentials are consistent with those recorded experimentally: the model-generated peripheral action potential has a more negative takeoff potential, faster upstroke, more positive peak value, prominent phase 1 repolarization, greater amplitude, shorter duration, and more negative maximum diastolic potential than the model-generated central action potential. In addition, the model peripheral cell shows faster pacemaking. The models behave qualitatively the same as tissue from the periphery and center of the SA node in response to block of tetrodotoxin-sensitive Na+current, L- and T-type Ca2+ currents, 4-aminopyridine-sensitive transient outward current, rapid and slow delayed rectifying K+ currents, and hyperpolarization-activated current. A one-dimensional model of a string of SA node tissue, incorporating regional heterogeneity, coupled to a string of atrial tissue has been constructed to simulate the behavior of the intact SA node. In the one-dimensional model, the spontaneous action potential initiated in the center propagates to the periphery at ∼0.06 m/s and then into the atrial muscle at 0.62 m/s.
Interleukin-1β, Src- and non-Src tyrosine kinases, and nitric oxide synthase induction in rat aorta in vitro
Authors: Gui Yu , Zheng Xi-Long , Hollenberg Morley D.
Published: December 2017

We studied the potential roles for endogenous interleukin-1β (IL-1β) and for several signaling pathways in the spontaneous induction in vitro of inducible nitric oxide synthase (iNOS) in endothelium-denuded rat aorta rings. Added IL-1β augmented, whereas the IL-1β receptor antagonist IL-1ra blocked, spontaneous iNOS induction. Furthermore, increases in IL-1β mRNA preceded those of iNOS mRNA. Mitogen-activated protein kinase kinase and phosphatidyl inositol 3′ kinase inhibition did not block iNOS induction, whereas nuclear factor κB inhibition did. The sarcoma virus tyrosine kinase (Src) family-selective inhibitor 4-amino-5(4-methylphenyl)-7-( t-butyl)pyrazolo[3,4-d]pyrimidine (PP1) blocked the upregulation of IL-1β mRNA and the subsequent induction of iNOS but not the induction of iNOS stimulated by exogenously added IL-1β. In contrast, the non-Src inhibitors TP 47/AG 213 and genistein and the tyrosine phosphatase inhibitor vanadate did not affect the spontaneous upregulation of IL-1β mRNA but blocked both the IL-1β-mediated and spontaneous induction of iNOS. We conclude that 1) the upregulation of tissue IL-1β, via a signaling pathway involving a Src family kinase, plays a key role in rat vascular iNOS induction and 2) non-Src tyrosine kinases play roles downstream from IL-1β for iNOS induction.
Matrix metalloproteinases and collagen ultrastructure in moderate myocardial ischemia and reperfusion in vivo
Authors: Lu Li , Gunja-Smith Zeenat , Woessner J. Frederick , Ursell Philip C. , Nissen Teo , Galardy Richard E. , Xu Ya , Zhu Peili , Schwartz Gregory G.
Published: December 2017

Severe ischemic injury or infarction of myocardium may cause activation of matrix metalloproteinases (MMPs) and damage the interstitial matrix. However, it is unknown whether MMP activation and matrix damage occur after moderate ischemia and reperfusion that result in myocardial stunning without infarction, and if so whether such changes contribute to postischemic myocardial expansion and contractile dysfunction. To address these questions, open-chest anesthetized pigs underwent 90 min of regional ischemia (subendocardial blood flow 0.4 ± 0.1 ml · g−1· min−1) and 90 min of reperfusion. After ischemia plus reperfusion, histological and ultrastructural examination revealed no myocardial infarction or inflammatory cell infiltration. Myocardial MMP-9 content increased threefold with a fourfold increase in the active form ( P < 0.001). Myocardial collagenase content doubled ( P < 0.01) but remained in latent form. MMP-2 and tissue inhibitors of metalloproteinases were unaffected. Despite increases in MMPs, collagen ultrastructure (assessed by cell maceration scanning electron microscopy) was unaltered. Intracoronary administration of the MMP inhibitor GM-2487 did not prevent or attenuate myocardial expansion (assessed by regional diastolic dimensions at near-zero left ventricular pressure) or contractile dysfunction. We conclude that although moderate ischemia and reperfusion alter myocardial MMP content and activity, these effects do not result in damage to interstitial collagen, nor do they contribute to myocardial expansion or contractile dysfunction.
Estimating oxygen transport resistance of the microvascular wall
Authors: Vadapalli Arjun , Pittman Roland N. , Popel Aleksander S.
Published: December 2017

The problem of diffusion of O2 across the endothelial surface in precapillary vessels and its utilization in the vascular wall remains unresolved. To establish a relationship between precapillary release of O2 and vascular wall consumption, we estimated the intravascular flux of O2 on the basis of published in vivo measurements. To interpret the data, we utilized a diffusion model of the vascular wall and computed possible physiological ranges for O2 consumption. We found that many flux values were not consistent with the diffusion model. We estimated the mitochondrial-based maximum O2 consumption of the vascular wall (Mmt) and a possible contribution to O2 consumption of nitric oxide production by endothelial cells (MNO). Many values of O2 consumption predicted from the diffusion model exceeded Mmt + MNO. In contrast, reported values of O2consumption for endothelial and smooth muscle cell suspensions and vascular strips in vitro do not exceed Mmt. We conjecture that most of the reported values of intravascular O2 flux are overestimated, and the likely source is in the experimental estimates of convective O2 transport at upstream and downstream points of unbranched vascular segments.
Heme oxygenase-1 is upregulated in the rat heart in response to chronic administration of angiotensin II
Authors: Ishizaka Nobukazu , Aizawa Toru , Mori Ichiro , Taguchi Jun-Ichi , Yazaki Yoshio , Nagai Ryozo , Ohno Minoru
Published: December 2017

Heme oxygenase (HO) is a heme-catabolizing enzyme that converts heme into biliverdin, iron, and carbon monoxide. HO-1, an inducible form of HO, is thought to act as an endogenous antioxidant defense mechanism. To determine whether chronic administration of angiotensin II affects HO-1 expression in the heart, expression and localization of HO-1 were investigated in the heart of rats receiving angiotensin II infusion (0.7 mg · kg−1· day−1) via osmotic minipump for up to 7 days. Angiotensin II induced formation of granulation tissue, characterized by myofibroblast proliferation, fibrous deposition, and inflammatory cell migration. Angiotensin II also upregulated cardiac HO-1 expression. Immunohistochemistry revealed that HO-1 was intensively expressed in the granulation tissue. The selective AT1-receptor antagonist, losartan, completely, but hydralazine only partially, suppressed angiotensin II-induced granulation tissue formation and HO-1 upregulation. Chronic norepinephrine infusion (2.8 mg · kg−1· day−1) did not induce granulation tissue formation or HO-1 upregulation. Our data suggest that angiotensin II upregulates cardiac HO-1 expression in the newly formed inflammatory lesion, which may represent an adaptive response to angiotensin II-induced cardiac damage.
Frequency modulation within electrocardiograms during ventricular fibrillation
Authors: Patwardhan Abhijit , Moghe Sachin , Wang Ke , Leonelli Fabio
Published: December 2017

Periods of reentrant activation and effective refractory periods are correlated with dominant frequency or reciprocal of cycle periods during ventricular fibrillation (VF). In the present study, we used an analysis technique based on Wigner transforms to quantify time-varying dominant frequencies in electrocardiograms (ECGs) during VF. We estimated dominant frequencies within orthogonal ECGs recorded in 10 dogs during trials of 10 s of VF and in 9 dogs during trials of 30 s of VF. In four additional dogs, we compared dominant frequencies during 10 s of VF before and after administration of amiodarone. Our results showed the following. 1) There was substantial frequency variation or modulation within the ECGs during 10 and 30 s of VF, the average variation being ±15% from the mean frequency. Amiodarone decreased mean frequencies ( P < 0.05) as expected; however, amiodarone also decreased the variation in frequencies ( P < 0.05). 2) During 30 s of VF, the dominant frequencies increased continuously from 7.3 to 8.1 Hz ( P < 0.05). The increase in frequency was almost linear with a rate of 0.022 Hz/s ( r 2 = 0.93, P < 0.0005). 3) Modulation of frequencies during the first and the last one-half of 30 s of VF was not different. Average (in time) mean frequencies and modulation of frequencies were similar in all three ECGs. 4) Although the averages were similar, during any VF episode, dominant frequencies in ECGs recorded from different locations on the body surface were similar to each other at some times and markedly different from each other at other times. We conclude that during VF, 1) frequencies in ECGs vary considerably and continuously, and amiodarone decreases this variation; 2) mean frequencies increase linearly during first 30 s; 3) the variability in frequency does not change during 30 s; and 4) at any given time, the frequencies within spatially different body surface ECGs can be either similar or markedly different.
Glucocorticoid pretreatment protects cardiac function and induces cardiac heat shock protein 72
Authors: Valen Guro , Kawakami Tsutomu , Tähepôld Peeter , Dumitrescu Alexandra , Löwbeer Christian , Vaage Jarle
Published: December 2017

Acute administration of glucocortiocoids reduces inflammation. Increasing knowledge of the mechanisms of action indicate that pretreatment with glucocorticoids could have organ-protective effects. We investigated whether pretreatment with methylprednisolone (MP) protected the heart against ischemia-reperfusion dysfunction, and we hypothetized that this protection might be due to induction of the cardioprotective heat shock protein 72 (HSP72). Rats were given vehicle or MP-40 mg/kg im as a double injection starting either 24 or 120 h (5 days) before their hearts were excised for Langendorff perfusion ( n = 6–11 hearts in each group). MP improved left ventricular function and coronary flow during reperfusion after 30 min of global ischemia and reduced infarct size. Cardiac HSP72 gradually increased in a 24-h time course after MP treatment, and the increase was sustained 5 days afterward (immunoblotting). HSP72 mRNA was either reduced or unchanged, indicating a posttranscriptional regulation. Pretreatment with hydrocortisone or dexamethasone ( n = 7–8 hearts of each) similarily increased cardiac HSP72 24 h afterward. This paper demonstrates that glucocorticoids increase cardiac HSP72 and protect organ function against ischemia-reperfusion injury.
Effects of adrenomedullin on load and myocardial performance in normal and heart-failure dogs
Authors: Lainchbury John G. , Meyer Donna M. , Jougasaki Michihisa , Burnett John C. , Redfield Margaret M.
Published: December 2017

Myocardial actions of the vasodilator peptide adrenomedullin (ADM) in the intact animal are unknown. Negative and positive inotropic actions have been reported in ex vivo experiments. Myocardial and load-altering actions of ADM in dogs before and after development of heart failure were studied. With controlled heart rate (atrial pacing) and after β-blockade, ADM was administered to five normal dogs in doses of 20 ng · kg−1 · min−1iv, 100 ng · kg−1 · min−1iv, and 200 ng · kg−1 · min−1into the left ventricle (LV). LV peak systolic pressure and end-systolic volume decreased with each dose of ADM. End-systolic pressure decreased with the two higher doses. At the highest dose, arterial elastance and the time constant of LV isovolumic relaxation (τ) decreased, and LV end-systolic elastance ( Ees) increased. LV end-diastolic pressure and volume were unchanged. In five additional normal dogs receiving only the highest dose of ADM (200 ng · kg−1 · min−1intra-LV), to control for increased heart rate and sympathetic activation observed with the cumulative infusion, ADM produced arterial vasodilation but no change in Eesor τ. In four dogs with pacing-induced heart failure, ADM (200 ng · kg−1 · min−1intra-LV) was without effect on τ, Ees, and systolic or diastolic pressure and volume. In vivo, ADM appears to be a selective arterial dilator without inotropic or lusitropic effects. The vasodilatory actions are attenuated in heart failure.
Development of vasomotor responses in fetal mesenteric arteries
Authors: Rouwet E. V. , De Mey J. G. R. , Slaaf D. W. , Heineman E. , Ramsay G. , Le Noble F. A. C.
Published: December 2017

Changes in mesenteric arterial diameters were studied using intravital microscopy in chick fetuses at days 13 and 17 of incubation, corresponding to 0.6 and 0.8 fetal incubation time, both during 5 min of hypoxia followed by 5 min of reoxygenation and after topical administration of increasing concentrations (10−6–10−2 M) of norepinephrine (NE) and acetylcholine (ACh). Baseline diameters of second-order mesenteric arteries increased from 56 μm at 0.6 incubation to 75 μm at 0.8 incubation. Acute hypoxia induced a reduction in arterial diameter to 87 ± 4.4% of baseline at 0.6 incubation and to 44 ± 6.7% at 0.8 incubation ( P< 0.01). During reoxygenation, mesenteric arteries dilated to 118 ± 6.5% and 121 ± 7.5% of baseline at 0.6 and 0.8 fetal incubation time, respectively. Phentolamine did not affect the vasoconstriction during hypoxia at 0.6 incubation, whereas this α-adrenergic antagonist significantly attenuated the vasoconstrictor response at 0.8 incubation (to 93 ± 2.7% of baseline, P < 0.01). Topical NE induced maximal vasoconstriction to 71 ± 3% of baseline at 0.6 incubation and to 35 ± 3.8% at 0.8 incubation ( P < 0.01). Maximal vasodilation to topical ACh was 113 ± 4.4% and 122 ± 4.8% of baseline at 0.6 and 0.8 incubation, respectively. These in vivo findings show that fetal mesenteric arteries constrict in response to acute hypoxia and that the increase in magnitude of this vasoconstrictor response from 0.6 to 0.8 of fetal development results from an increase in adrenergic constrictor capacity.
Metabolic evidence for sequestration of low-density lipoprotein in abdominal aorta of normal rabbits
Authors: Schwenke Dawn C.
Published: December 2017

In rabbits, atherosclerosis develops preferentially at branch sites compared with the adjacent uniform aorta. This study investigated the hypothesis that low-density lipoprotein (LDL) is “sequestered” (present in a form that exchanges slowly with plasma LDL) in the aortas of normal rabbits and that more LDL is sequestered at branch sites. Thus 33 normal rabbits were injected with LDL labeled with125I-labeled tyramine cellobiose (125I-TC) to trace both undegraded LDL and aortic LDL degradation products. For 25 rabbits, LDL was also labeled with131I to trace undegraded LDL alone. The time-dependent aortic125I-TC and131I accumulation was determined from 0.6 to 120 h after injection. Compartmental modeling provided metabolic evidence for sequestration of LDL at the branch ( P < 0.01) and uniform ( P < 0.005) abdominal aorta. Concentrations of sequestered LDL were 109 ± 28% higher ( P < 0.0005) for branch sites. LDL mean residence time was 23.5 ± 3.1 h for branch sites, 7.6 ± 3.5 h longer ( P < 0.05) than for the uniform abdominal aorta. Enhanced retention of higher concentrations of sequestered LDL at branch sites could account for the increased susceptibility of these aortic sites to atherosclerosis.
Dissociation of muscle sympathetic nerve activity and leg vascular resistance in humans
Authors: Shoemaker J. Kevin , Herr Michael D. , Sinoway Lawrence I.
Published: December 2017

We examined the hypothesis that the increase in inactive leg vascular resistance during forearm metaboreflex activation is dissociated from muscle sympathetic nerve activity (MSNA). MSNA (microneurography), femoral artery mean blood velocity (FAMBV, Doppler), mean arterial pressure (MAP), and heart rate (HR) were assessed during fatiguing static handgrip exercise (SHG, 2 min) followed by posthandgrip ischemia (PHI, 2 min). Whereas both MAP and MSNA increase during SHG, the transition from SHG to PHI is characterized by a transient reduction in MAP but sustained elevation in MSNA, facilitating separation of these factors in vivo. Femoral artery vascular resistance (FAVR) was calculated (MAP/MBV). MSNA increased by 59 ± 20% above baseline during SHG ( P < 0.05) and was 58 ± 18 and 78 ± 18% above baseline at 10 and 20 s of PHI, respectively ( P < 0.05 vs. baseline). Compared with baseline, FAVR increased 51 ± 22% during SHG ( P < 0.0001) but returned to baseline levels during the first 30 s of PHI, reflecting the changes in MAP ( P < 0.005) and not MSNA. It was concluded that control of leg muscle vascular resistance is sensitive to changes in arterial pressure and can be dissociated from sympathetic factors.
Ratiometry of transmembrane voltage-sensitive fluorescent dye emission in hearts
Authors: Knisley Stephen B. , Justice Robert K. , Kong Wei , Johnson Philip L.
Published: December 2017

Transmembrane voltage-sensitive fluorescence measurements are limited by baseline drift that can obscure changes in resting membrane potential and by motion artifacts that can obscure repolarization. Voltage-dependent shift of emission wavelengths may allow reduction of drift and motion artifacts by emission ratiometry. We have tested this for action potentials and potassium-induced changes in resting membrane potential in rabbit hearts stained with di-4-ANEPPS [Pyridinium, 4-(2-(6-(dibutylamino)-2-naphthalenyl) ethenyl)-1-(3-sulfopropyl)-, hydroxide, inner salt] using laser excitation (488 nm) and a two-photomultiplier tube system or spectrofluorometer (resolution of 500–1,000 Hz and <1 mm). Green and red emissions produced upright and inverted action potentials, respectively. Ratios of green emission to red emission followed action potential contours and exhibited larger fractional changes than either emission alone ( P < 0.001). The largest changes and signal-to-noise ratio (signal/noise) were obtained with numerator wavelengths of 525–550 nm and denominator wavelengths of 650–700 nm. Ratiometry lessened drift 56–66% ( P < 0.015) and indicated decreases in resting membrane potential. Ratiometry lessened motion artifacts and increased magnitudes of deflections representing phase-zero depolarizations relative to total deflections by 123–188% in intact hearts ( P < 0.02). Durations of action potentials at different pacing rates, temperatures, and potassium concentrations were independent of whether they were measured ratiometrically or with microelectrodes ( P ≥ 0.65). The ratiometric calibration slope was 0.017/100 mV and decreased with time. Thus emission ratiometry lessens the effects of motion and drift and indicates resting membrane potential changes and repolarization.
Effects of pinacidil on coronary Ca2+-myosin phosphorylation in cold potassium cardioplegia model
Authors: Matsuda Naruto , Morgan Kathleen G. , Sellke Frank W.
Published: December 2017

The effects of the potassium (K+) channel opener pinacidil (Pin) on the coronary smooth muscle Ca2+-myosin light chain (MLC) phosphorylation pathway under hypothermic K+cardioplegia were determined by use of an in vitro microvessel model. Rat coronary arterioles (100–260 μm in diameter) were subjected to 60 min of simulated hypothermic (20°C) K+cardioplegic solutions (K+= 25 mM). We first characterized the time course of changes in intracellular Ca2+concentration, MLC phosphorylation, and diameter and observed that the K+cardioplegia-related vasoconstriction was associated with an activation of the Ca2+-MLC phosphorylation pathway. Supplementation with Pin effectively suppressed the Ca2+accumulation and MLC phosphorylation in a dose-dependent manner and subsequently maintained a small decrease in vasomotor tone. The ATP-sensitive K+(KATP)-channel blocker glibenclamide, but not the nitric oxide (NO) synthase inhibitor Nω-nitro-l-arginine methyl ester, significantly inhibited the effect of Pin. K+cardioplegia augments the coronary Ca2+-MLC pathway and results in vasoconstriction. Pin effectively prevents the activation of this pathway and maintains adequate vasorelaxation during K+cardioplegia through a KATP-channel mechanism not coupled with the endothelium-derived NO signaling cascade.
Molecular dimensions of Hb-based O2carriers determine constriction of resistance arteries and hypertension
Authors: Sakai Hiromi , Hara Hiroyuki , Yuasa Minako , Tsai Amy G. , Takeoka Shinji , Tsuchida Eishun , Intaglietta Marcos
Published: December 2017

The effect of molecular dimension of hemoglobin (Hb)-based O2carriers on the diameter of resistance arteries ( A0, 158 ± 21 μm) and arterial blood pressure were studied in the conscious hamster dorsal skinfold model. Cross-linked Hb (XLHb), polyethylene glycol (PEG)-conjugated Hb, hydroxyethylstarch-conjugated XLHb, polymerized XLHb, and PEG-modified Hb vesicles (PEG-HbV) were synthesized. Their molecular diameters were 7, 22, 47, 68, and 224 nm, respectively. The bolus infusion of 7 ml/kg of XLHb (5 g/dl) caused an immediate hypertension (+34 ± 13 mmHg at 3 h) with a simultaneous decrease in A0diameter (79 ± 8% of basal value) and a blood flow decrease throughout the microvascular network. The diameter of smaller arterioles did not change significantly. Infusion of larger O2carriers resulted in lesser vasoconstriction and hypertension, with PEG-HbV showing the smallest changes. Constriction of resistance arteries was found to be correlated with the level of hypertension, and the responses were proportional to the molecular dimensions of the O2carriers. The underlying mechanism is not evident from these experiments; however, it is likely that the effects are related to the diffusion properties of the different Hb molecules.
Endothelial adenosine transporter characterization in perfused guinea pig hearts
Authors: Schwartz Lisa M. , Bukowski Thomas R. , Ploger James D. , Bassingthwaighte James B.
Published: December 2017

Adenosine (Ado), a smooth muscle vasodilator and modulator of cardiac function, is taken up by many cell types via a saturable transporter, blockable by dipyridamole. To quantitate the influences of endothelial cells in governing the blood-tissue exchange of Ado and its concentration in the interstitial fluid, one must define the permeability-surface area products ( PS) for Ado via passive transport through interendothelial gaps [ PS g(Ado)] and across the endothelial cell luminal membrane ( PS ecl) in their normal in vivo setting. With the use of the multiple-indicator dilution (MID) technique in Krebs-Ringer perfused, isolated guinea pig hearts (preserving endothelial myocyte geometry) and by separating Ado metabolites by HPLC, we found permeability-surface area products for an extracellular solute, sucrose, via passive transport through interendothelial gaps [ PS g(Suc)] to be 1.9 ± 0.6 ml · g−1 · min−1( n = 16 MID curves in 4 hearts) and took PS g(Ado) to be 1.2 times PS g(Suc). MID curves were obtained with background nontracer Ado concentrations up to 800 μm, partially saturating the transporter and reducing its effective PS ecl for Ado. The estimated maximum value for PS ecl in the absence of background adenosine was 1.1 ± 0.1 ml · g−1 · min−1 [maximum rate of transporter conformational change to move the substrate from one side of the membrane to the other (maximal velocity; V max) times surface area of 125 ± 11 nmol · g−1 · min−1], and the Michaelis-Menten constant ( K m) was 114 ± 12 μM, where ± indicates 95% confidence limits. Physiologically, only high Ado release with hypoxia or ischemia will partially saturate the transporter.
Hypoxic pulmonary vasoconstriction is modified byP-450 metabolites
Authors: Zhu Daling , Birks Eric K. , Dawson Christopher A. , Patel Monica , Falck John R. , Presberg Kenneth , Roman Richard J. , Jacobs Elizabeth R.
Published: December 2017

20-Hydroxyeicosatetraenoic acid (20-HETE) is a cytochrome P-450 4A (CYP4A) metabolite of arachidonic acid (AA) in human and rabbit lung microsomes and is a dilator of isolated human pulmonary arteries (PA). However, little is known regarding the contribution of P-450 metabolites to pulmonary vascular tone. We examined 1) the effect of two mechanistically distinct ω- and ω1-hydroxylase inhibitors on perfusion pressures in isolated rabbit lungs ventilated with normoxic or hypoxic gases, 2) changes in rabbit PA ring tone elicited by 20-HETE or ω- and ω1-hydroxylase inhibitors, and 3) expression of CYP4A protein in lung tissue. A modest increase in perfusion pressure (55 ± 11% above normoxic conditions) was observed in isolated perfused lungs during ventilation with hypoxic gas (FiO2= 0.05). Inhibitors of 20-HETE synthesis, 17-oxydecanoic acid (17-ODYA) or N-methylsulfonyl-12,12-dibromododec-11-enamide (DDMS), increased baseline perfusion pressure above that of vehicle and amplified hypoxia-induced increases in perfusion pressures by 92 ± 11% and 105 ± 11% over baseline pressures, respectively. 20-HETE relaxed phenylephrine (PE)-constricted PA rings. Treatment with 17-ODYA enhanced PE-induced contraction of PA rings, consistent with inhibition of a product that promotes arterial relaxation, whereas 6-(20-propargyloxyphenyl)hexanoic acid (PPOH), an epoxygenase inhibitor, blunted contraction to PE. Conversion of AA into 20-HETE was blocked by 17-ODYA, DDMS, and hypoxia. CYP4A immunospecific protein confirms expression of CYP4A in male rabbit lung tissue. Our data suggest that endogenously produced 20-HETE could modify rabbit pulmonary vascular tone, particularly under hypoxic conditions.
Orthostatic hypotension in aging humans
Authors: Shi Xiangrong , Wray D. Walter , Formes Kevin J. , Wang Hong-Wei , Hayes Patrick M. , O-Yurvati Albert H. , Weiss Martin S. , Reese I. Philip
Published: December 2017

We tested the hypothesis that hypotension occurred in older adults at the onset of orthostatic challenge as a result of vagal dysfunction. Responses of heart rate (HR) and mean arterial pressure (MAP) were compared between 10 healthy older and younger adults during onset and sustained lower body negative pressure (LBNP). A younger group was also assessed after blockade of the parasympathetic nervous system with the use of atropine or glycopyrrolate and after blockade of the β1-adrenoceptor by use of metoprolol. Baseline HR (older vs. younger: 59 ± 4 vs. 54 ± 1 beats/min) and MAP (83 ± 2 vs. 89 ± 3 mmHg) were not significantly different between the groups. During −40 Torr, significant tachycardia occurred at the first HR response in the younger subjects without hypotension, whereas significant hypotension [change in MAP (ΔMAP) −7 ± 2 mmHg] was observed in the elderly without tachycardia. After the parasympathetic blockade, tachycardiac responses of younger subjects were diminished and associated with a significant hypotension at the onset of LBNP. However, MAP was not affected after the cardiac sympathetic blockade. We concluded that the elderly experienced orthostatic hypotension at the onset of orthostatic challenge because of a diminished HR response. However, an augmented vasoconstriction helped with the maintenance of their blood pressure during sustained LBNP.
Model of structural and functional adaptation of small conductance vessels to arterial hypotension
Authors: Quick Christopher M. , Young William L. , Leonard Edward F. , Joshi Shailendra , Gao Erzhen , Hashimoto Tomoki
Published: December 2017

Vascular networks adapt structurally in response to local pressure and flow and functionally in response to the changing needs of tissue. Whereas most research has either focused on adaptation of the macrocirculation, which primarily transports blood, or the microcirculation, which primarily controls flow, the present work addresses adaptation of the small conductance vessels in between, which both conduct blood and resist flow. A simple hemodynamic model is introduced consisting of three parts: 1) bifurcating arterial and venous trees, 2) an empirical description of the microvasculature, and 3) a target shear stress depending on pressure. This simple model has the minimum requirements to explain qualitatively the observed structure in normotensive conditions. It illustrates that flow regulation in the microvasculature makes adaptation in the larger conductance vessels stable. Furthermore, it suggests that structural changes in response to hypotension can account for the observed decrease in the lower limit of autoregulation in chronically hypotensive vasculature. Independent adaptation to local conditions thus yields a coordinated set of structural changes that ultimately adapts supply to demand.
Mechanisms of calcitonin gene-related peptide-induced increases of pulmonary blood flow in fetal sheep
Authors: Takahashi Yasushi , De Vroomen Maartje , Roman Christine , Heymann Michael A.
Published: December 2017

Fetal pulmonary blood flow is regulated by various vasoactive substances. One, calcitonin gene-related peptide (CGRP), increases pulmonary blood flow. We examined four key physiological mechanisms underlying this response using the blocker drugs CGRP receptor blocker (CGRP8–37), nitric oxide synthase inhibitor [ N ω-nitro-l-arginine (l-NNA)], adenosine triphosphate-dependent potassium (KATP) channel blocker (glibenclamide), and cyclooxygenase inhibitor (indomethacin) in 17 near-term fetal sheep. Catheters were placed in the left (LPA) and main pulmonary arteries, and an ultrasonic flow transducer was placed around the LPA to measure flow continuously. CGRP was injected directly into the LPA (mean 1.02 μg/kg) before and after blockade, and responses to CGRP were statistically compared. Before blockade, CGRP increased LPA blood flow from 23 ± 25 to 145 ± 77 ml/min (means ± SD), and these increases were significantly attenuated by CGRP8–37( n = 6; 91% inhibition), l-NNA ( n = 6; 86% inhibition), and glibenclamide ( n = 6; 69% inhibition). No significant changes were found with indomethacin ( n = 6; 4% inhibition). Thus, in the fetal pulmonary circulation, CGRP increases pulmonary blood flow not only through its specific receptor but also, in part, through nitric oxide release and KATP channel activation.