bluuebunny/crossref_metadata_2025 huggingface dataset:
Dilatation of the ductus venosus in human fetuses: ultrasonographic evidence and mathematical modeling
Authors: Bellotti M. , Pennati G. , Pardi G. , Fumero R.
Published: December 2017

Autonomic regulation of blood flow through the fetal ductus venosus has been suggested, but the existence of a sphincter at the ductal entrance in human fetuses has yet to be established. In this paper two cases of apparent ductus venosus dilatation in two growth-restricted human fetuses are reported. Prolonged ultrasonographic analysis (45 min) showed rapid and substantial changes (>80%) of ductal diameters. Pulsed Doppler analysis was used to investigate flow velocity in the ductus venosus and umbilical vein for both normal and dilated conditions. Dilated conditions caused manifest modifications of velocity tracings. Systolic peak velocity in the ductus did not change visibly, whereas velocity at the atrial contraction showed evident reduction; consequently, pulsatility indexes increased. Furthermore, the umbilical vein presented flow velocity pulsations. The mean blood flow rate through the ductus seemed to increase substantially (>70%) for high dilatation. To investigate these findings further, we performed simulations of ductal dilatation by means of a lumped-parameter mathematical model of the human fetal circulation. Model results agreed with clinical evidence and confirmed the relationship between ductal dilatation and the observed velocity alterations. Simulated systolic peak velocity slightly increased for small dilatation (<30%), whereas atrial velocity was reduced when the ductus dilated. Furthermore, the model indicated that umbilical venous pressure decreases for increasing dilatation, whereas no change occurs in the central venous pressure. The present results seem to indicate the presence of active dilatation of the ductus venosus in human fetuses.
Influence of prior Na+pump activity on pump and Na+/Ca2+exchange currents in mouse ventricular myocytes
Authors: Su Zhi , Zou Anruo , Nonaka Akihiko , Zubair Iram , Sanguinetti Michael C. , Barry William H.
Published: December 2017

We examined the dependence of peak Na+pump and Na+/Ca2+exchanger currents on prior Na+pump inhibition induced by exposure to zero extracellular K+in voltage-clamped adult murine ventricular myocytes. Abrupt activation of the Na+pump by reexposure of myocytes to extracellular K+with a rapid solution switcher resulted in the development of a transient peak current at ∼500 ms, followed by a decline over 1–2 min to a steady-state level. The magnitudes of both the peak Na+pump current ( Ip) and the peak outward Na+/Ca2+exchange current, activated by rapidly reducing extracellular Na+to zero with the solution switcher, were dependent on previous Na+pump activity. [Na+] gradients (Na+-binding benzofuran isophthalate fluorescence) between the patch pipette and the bulk cytosol were relatively small and could not account for the large differences between peak and steady-state Ipand reverse Na+/Ca2+exchanger currents. Our results are consistent with the presence of a subsarcolemmal Na+concentration gradient, which is similar for the Na+pump and the Na+/Ca2+exchanger. These findings also support the hypothesis that the Na+pump and the Na+/Ca2+exchanger are colocalized in the sarcolemma.
A load-independent in vivo model for evaluating therapeutic interventions in injured myocardium
Authors: Lewis Cleveland W. , Atkins B. Zane , Hutcheson Kelley A. , Gillen Christian T. , Reedy Mary C. , Glower Donald D. , Taylor Doris A.
Published: December 2017

Although cardiomyocyte damage is normally irreversible, gene therapy and somatic cell transfer offer potential for improving function in damaged regions of the heart. However, in ischemic models of injury, variability in depth, size, and location of damage compromises statistical evaluation of in vivo function. We have adapted cryoablation to create a reproducible, posterior, transmural lesion within rabbit myocardium in which small changes in function are measurable in vivo. Before and at 2 and 6 wk postinjury, in vivo left ventricular intracavitary pressure and myocardial segment length were measured. Regional indexes of performance, segmental stroke work (SW), and percent systolic shortening (SS) were significantly decreased ( P < 0.001) postcryoinjury as was the slope ( Mw) of the linear preload recruitable SW relationship between SW and end-diastolic segment length ( P = 0.0001). Decreased SW, SS, and Mwcorrelated with wall thinning, loss of myocytes, presence of fibroblasts, and transmural scar formation. Reproducible changes in regional myocardial performance in vivo postcryoinjury suggest that this is a reasonable model for evaluating novel therapies for cardiovascular disease.
Letters to the Editor
Authors: Efimov Igor R.
Published: December 2017

The following is an abstract of the article discussed in the subsequent letter:

 Choi, Bum-Rak, and Guy Salama. Optical mapping of atrioventricular node reveals a conduction barrier between atrial and nodal cells. Am. J. Physiol. 274 ( Heart Circ. Physiol. 43): H829–H845, 1998.—The mechanisms responsible for atrioventricular (AV) delay remain unclear, in part due to the inability to map electrical activity by conventional microelectrode techniques. In this study, voltage-sensitive dyes and imaging techniques were refined to detect action potentials (APs) from the small cells comprising the AV node and to map activation from the “compact” node. Optical APs (124) were recorded from 5 × 5 mm (∼0.5-mm depth) AV zones of perfused rabbit hearts stained with a voltage-sensitive dye. Signals from the node exhibited a set of three spikes; the first and third ( peaks Iand III) were coincident with atrial (A) and ventricular (V) electrograms, respectively. The second spike ( peak II)represented the firing of midnodal (N) and/or lower nodal (NH) cell APs as indicated by their small amplitude, propagation pattern, location determined from superimposition of activation maps and histological sections of the node region, dependence on depth of focus, and insensitivity to tetrodotoxin (TTX). AV delays consisted of τ1 (49.5 ± 6.59 ms, 300-ms cycle length), the interval between peaks I and II (perhaps AN to N cells), and τ2 (57.57 ± 5.15 ms), the interval between peaks II and III (N to V cells). The conductance time across the node was 10.33 ± 3.21 ms, indicating an apparent conduction velocity (ΘN) of 0.162 ± 0.02 m/s ( n = 9) that was insensitive to TTX. In contrast, τ1 correlated with changes in AV node delays (measured with surface electrodes) caused by changes in heart rate or perfusion with acetylcholine. The data provide the first maps of activation across the AV node and demonstrate that ΘN is faster than previously presumed. These findings are inconsistent with theories of decremental conduction and prove the existence of a conduction barrier between the atrium and the AV node that is an important determinant of AV node delay.
Isolation and characterization of the human gene encodingI to: further diversity by alternative mRNA splicing
Authors: Kong Wei , Po Sunny , Yamagishi Toshio , Ashen M. Dominique , Stetten Gail , Tomaselli Gordon F.
Published: December 2017

The transient outward K+ current ( I to) in the heart is responsible for the initial phase of repolarization and for setting the plateau voltage of the ventricular action potential. Recently, Kv4.3 has emerged as the leading candidate α-subunit gene that underlies I to in larger mammals such as dogs and humans. We have cloned the human Kv4.3 homolog and describe a carboxyl-terminal splice variant that inserts 19 amino acids with a consensus protein kinase C (PKC) phosphorylation site into the protein after the last membrane-spanning segment. The coding region of Kv4.3 is comprised of at least five exons and is located on chromosome 1p13.3. In the basal state the basic biophysical properties of both of the splice variants are identical.
I NaCa andI Cl(Ca)contribute to isoproterenol-induced delayed afterdepolarizations in midmyocardial cells
Authors: Zygmunt Andrew C. , Goodrow Robert J. , Weigel Charlene M.
Published: December 2017

The contributions of electrogenic sodium/calcium exchange current ( I NaCa), calcium-activated chloride conductance [ I Cl(Ca)], and calcium-activated nonselective cation conductance to delayed afterdepolarizations (DAD) were examined. Nonselective cation channels were absent in canine M cells, since inhibition of I NaCa and I Cl(Ca)eliminated all calcium-activated currents without abolishing cell shortening. After the cells were treated with isoproterenol and ouabain to increase calcium loading, I NaCa was 168 ± 30 × 10−3 pC/pF and I Cl(Ca) was 114 ± 24 × 10−3pC/pF. Transient overlapping inward and outward currents were evoked positive to the chloride reversal potential ( E Cl). Outward current was chloride sensitive, and inward current was blocked by replacement of external sodium with lithium. When E Cl was −50 mV, triggered activity occurred in normal external sodium and persisted after inhibition of I NaCa. Steps to −80 mV revealed oscillating inward currents in normal sodium and chloride, which persisted after inhibition of I NaCa. When E Cl was equal to −113 mV, I Cl(Ca) opposed I NaCa at the resting potential. DAD occurred in normal sodium, and inhibition of outward I Cl(Ca)provoked triggered activity. We conclude that I NaCa represents ∼60% of the total calcium-activated current at resting potentials but that both I NaCa and I Cl(Ca) work in concert to cause DAD in calcium-overloaded cells.
Lack of desensitization and enhanced efficiency of calcium channel promoter in conscious dogs with heart failure
Authors: Asai Kuniya , Uechi Masami , Sato Naoki , Shen Weiqun , Meguro Tomomi , Mathier Michael A. , Shannon Richard P. , Vatner Stephen F.
Published: December 2017

The goal of this study was to compare responses to a calcium promoter, BAY y 5959, and dobutamine (Dob) in heart failure (HF). Dogs ( n = 9) were chronically instrumented and studied in the conscious state before and after pacing-induced HF. In the control state, BAY y 5959 (20 μg ⋅ kg−1 ⋅ min−1) increased the first derivative of left ventricular (LV) pressure (dP/d t) by 83 ± 8% and mean arterial pressure (MAP) by 8 ± 2% and decreased heart rate (HR) by 30 ± 3%. With Dob (10 μg ⋅ kg−1 ⋅ min−1) LV dP/d t rose similarly (+80 ± 6%), but HR also rose (+25 ± 4%) ( P < 0.05 vs. BAY y 5959). After HF developed, BAY y 5959 still increased LV dP/d t by 108 ± 8% and MAP by 21 ± 2% and decreased HR by 28 ± 4%, whereas Dob increased LV dP/d t by only 50 ± 7% ( P < 0.05 vs. BAY y 5959) and MAP by 7 ± 3%, and HR did not change (+3 ± 3%) ( P < 0.05 vs. BAY y 5959). In HF, cardiac work increased more ( P < 0.05) with BAY y 5959 (+105 ± 13%) compared with Dob (+47 ± 11%), yet myocardial oxygen consumption increased similarly with the two drugs. Accordingly, mechanical efficiency increased more ( P < 0.05) with BAY y 5959 (+73 ± 14%) than with Dob (+17 ± 12%). These data indicate that 1) increases in contractility mediated directly by Ca2+ are relatively resistant to desensitization in HF; and 2) the calcium-channel promoter can produce increases in myocardial contractility and cardiac work similar to those of Dob at a significantly lower oxygen cost, thereby enhancing mechanical efficiency in HF.
Relation between zero-stress state and branching order of porcine left coronary arterial tree
Authors: Frøbert Ole , Gregersen Hans , Bjerre Jesper , Bagger Jens P. , Kassab Ghassan S.
Published: December 2017

The left common coronary arterial trees of eight pig hearts were dissected. The zero-stress state (the state of the organ when the external loads are removed) of the coronary arteries was determined by first cutting the arteries into short, ring-shaped segments perpendicular to the longitudinal axis of the blood vessel and then making a radial cut. This procedure caused the ring to open into a sector whose opening angle (θ), internal and external lengths (circumferences), and wall thickness were measured. Morphometric and θ data were organized in the framework of a diameter-defined Strahler system. We investigated 4 rings from the left common coronary artery (LCCA), 185 from the left anterior descending artery (LAD) and its branches, and 159 from the left circumflex artery (LCX) and its branches. The inner circumferences of the rings ranged over six orders for the LAD arterial tree and five orders for the LCX arterial tree, corresponding to a diameter range of about one order of magnitude for both arteries. θ demonstrates viscoelastic behavior and was measured 30 min after cutting. Our results show that the inner and outer circumference and the wall thickness increase as geometric sequences with the order number. θ is found to decrease linearly toward the smaller orders with a slope of 7.3°/order in the range of the six largest orders. Strain calculations showed that the inner part of the arterial wall is in compression, whereas the outer part of the wall is in tension in the no-load (zero transmural pressure) state. This study provides basic data on the zero-stress state that are necessary for understanding the mechanics of the coronary artery.
Histological validation of myocardial microstructure obtained from diffusion tensor magnetic resonance imaging
Authors: Scollan D. F. , Holmes Alex , Winslow Raimond , Forder John
Published: December 2017

Diffusion tensor magnetic resonance imaging (MRI) is a possible new means of elucidating the anatomic structure of the myocardium. It enjoys several advantages over traditional histological approaches, including the ability to rapidly measure fiber organization in isolated, perfused, arrested hearts, thereby avoiding fixation and sectioning of artifacts. However, quantitative validation of this MRI method has been lacking. Here, fiber orientations estimated in the same locations in the same heart using both diffusion tensor MRI and histology are compared in a total of two perfused rabbit hearts. Fiber orientations were statistically similar for both methods and differed on average by 12° at any single location. This is similar to the 10° uncertainty in fiber orientation achieved with histology. In addition, imaging studies performed in a total of seven hearts support a level of organization beyond the myofiber, the recently described laminar organization of the ventricular myocardium.
Limb reduction defects in endothelial nitric oxide synthase-deficient mice
Authors: Gregg Anthony R. , Schauer Anita , Shi Ou , Liu Zhouwen , Lee Caroline G. L. , O’Brien William E.
Published: December 2017

Nitric oxide synthases are a family of enzymes capable of converting l-arginine to l-citrulline with the subsequent release of nitric oxide (NO). NO has been shown to have multiple biologic effects depending on the isoform responsible for its production and its tissue of origin. Murine endothelial nitric oxide synthase (eNOS) is encoded by Nos3, located on mouse chromosome 5. NO produced from this isoform causes vascular smooth muscle relaxation. Other investigators have shown that the administration of nonspecific inhibitors of nitric oxide synthases to pregnant rats induces limb reduction defects. However, mice deficient in Nos3 have not previously been noted to show such abnormalities. To explore the importance of eNOS during development, we produced mice deficient in eNOS using embryonic stem cell technology. Limb reduction defects were seen in ∼10% of the null animals. We also observed increased neonatal loss of homozygous deficient pups. One functional copy of Nos3 eliminates the risk of limb defects observed in our mouse strain. These findings have implications for understanding genetic predisposition to sporadic limb reduction defects in humans.
Chronic circadian desynchronization decreases the survival of animals with cardiomyopathic heart disease
Authors: Penev Plamen D. , Kolker Daniel E. , Zee Phyllis C. , Turek Fred W.
Published: December 2017

Shift work is associated with increased cardiovascular morbidity and mortality. Whereas it has been suggested that continuous shifting of the circadian clock/sleep-wake cycle may have negative effects on health, there is very little experimental evidence to support such a hypothesis. Cardiomyopathic Syrian hamsters were either maintained on a fixed light-dark (LD) cycle ( n = 31) or were subjected to a 12-h phase shift in the LD cycle on a weekly basis ( n = 32). The duration of the life span was recorded for each animal. Chronic reversal of the external LD cycle at weekly intervals resulted in a significant decrease in the survival time in cardiomyopathic hamsters with the median life span being reduced by 11%. Disrupting normal circadian rhythmicity in an animal susceptible to early mortality due to cardiac disease results in a further decrease in longevity. The deleterious effects of the chronic phase shifts in the LD cycle in cardiomyopathic hamsters may be related to reports of increased cardiovascular morbidity and mortality in humans engaged in shift work.
Effects of sympathetic nerve stimulation on membrane potential, [Ca2+]i, and force in the toad sinus venosus
Authors: Bramich Narelle J. , Cousins Helen M.
Published: December 2017

The effects of sympathetic nerve stimulation on beat rate, force, intracellular Ca2+concentration ([Ca2+]i) measured using fura 2, and membrane potential were recorded from the spontaneously beating toad sinus venosus. Short trains of stimuli evoked an increase in the beat rate and force. During this tachycardia the amplitude of pacemaker action potentials was not changed, but there was an increase in the basal level of [Ca2+]iwith little change in peak [Ca2+]imeasured during each action potential. Depletion of intracellular Ca2+stores with caffeine (3 mM) abolished all responses to sympathetic nerve stimulation. The effects of caffeine were fully reversible. Caffeine (3 mM), in the presence of the Ca2+-ATPase inhibitor thapsigargin (30 μM), abolished irreversibly the chronotropic and inotropic responses evoked by sympathetic nerve stimulation. Ryanodine (10 μM) attenuated, but did not abolish, these responses. These results suggest that, in the toad sinus venosus, increases in force and beat rate evoked by sympathetic nerve stimulation result from the release of Ca2+from intracellular Ca2+stores.
New simple methods for isolating baroreceptor regions of carotid sinus and aortic depressor nerves in rats
Authors: Sato Takayuki , Kawada Toru , Miyano Hiroshi , Shishido Toshiaki , Inagaki Masashi , Yoshimura Ryoichi , Tatewaki Teiji , Sugimachi Masaru , Alexander Joe , Sunagawa Kenji
Published: December 2017

We developed new methods for isolating in situ baroreceptor regions of carotid sinus and aortic depressor nerves in halothane-anesthetized rats. After ligation of the root of the external carotid artery, the internal carotid and pterygopalatine arteries were embolized with two ball bearings of 0.8 mm in diameter. Bilateral carotid sinus pressures were changed between 60 and 180 mmHg in 20-mmHg steps lasting 1 min each. The sigmoidal steady-state relationship between aortic and carotid sinus pressures in 11 rats indicated the maximum gain of the carotid sinus baroreflex to be −2.99 ± 0.75 at 120 ± 5 mmHg. An in situ isolation of the baroreceptor area of the right aortic depressor nerve could be made by ligation of the innominate, common carotid, and subclavian arteries in 9 rats. Pressure imposed on the subclavian baroreceptor was altered between 40 and 180 mmHg in 20-mmHg steps lasting 1 min each. The sigmoidal steady-state relationship between the aortic depressor nerve activity and imposed pressure showed that the baroreceptor gain peaked at 118 ± 4 mmHg. We established an easy approach to the rat baroreflex and baroreceptor research.
Subcellular localization of the Na+/H+exchanger NHE1 in rat myocardium
Authors: Petrecca Kevin , Atanasiu Roxana , Grinstein Sergio , Orlowski John , Shrier Alvin
Published: December 2017

The Na+/H+exchanger NHE1 isoform is an integral component of cardiac intracellular pH homeostasis that is critically important for myocardial contractility. To gain further insight into its physiological significance, we determined its cellular distribution in adult rat heart by using immunohistochemistry and confocal microscopy. NHE1 was localized predominantly at the intercalated disk regions in close proximity to the gap junction protein connexin 43 of atrial and ventricular muscle cells. Significant labeling of NHE1 was also observed along the transverse tubular systems, but not the lateral sarcolemmal membranes, of both cell types. In contrast, the Na+-K+-ATPase α1-subunit was readily labeled by a specific mouse monoclonal antibody (McK1) along the entire ventricular sarcolemma and intercalated disks and, to a lesser extent, in the transverse tubules. These results indicate that NHE1 has a distinct distribution in heart and may fulfill specialized roles by selectively regulating the pH microenvironment of pH-sensitive proteins at the intercalated disks (e.g., connexin 43) and near the cytosolic surface of sarcoplasmic reticulum cisternae (e.g., ryanodine receptor), thereby influencing impulse conduction and excitation-contraction coupling.
Cadherin-5 redistribution at sites of TNF-α and IFN-γ-induced permeability in mesenteric venules
Authors: Wong Raymond K. , Baldwin Ann L. , Heimark Ronald L.
Published: December 2017

The response of the endothelial permeability barrier in microvascular networks of the rat mesentery to perfused immune inflammatory cytokines tumor necrosis factor-α (TNF-α) and interferon-γ (IFN-γ) was examined. TNF-α (12.5 U/ml) treatment did not change albumin permeability, but in combination with IFN-γ (20 U/ml), there was a marked increase in the number of sites of extravascular albumin in postcapillary venules. Endothelial integrity was characterized by cadherin-5 immunoreactivity, which was localized to the continuous intercellular junctions of endothelium in arterioles, capillaries, and venules. Perfusion with the combined cytokines showed that the increased albumin permeability was dose dependent and correlated with the focal disorganization of cadherin-5 at intercellular junctions of venular endothelium. No correlation was found between the increase in albumin permeability and the localization of intravascular leukocytes or extravascular mast cells. These results show that the combination of TNF-α and IFN-γ induces an endothelial phenotype with focal loss of cadherin-5 intercellular adhesion, which, in part, facilitates passage of blood macromolecules and cells to the interstitium.
Presence of hemoglobin inside aortic endothelial cells after cell-free hemoglobin administration in guinea pigs
Authors: Faivre-Fiorina Béatrice , Caron Alexis , Fassot Céline , Fries Isabelle , Menu Patrick , Labrude Pierre , Vigneron Claude
Published: December 2017

The endothelium is the production site of several potent vasoactive factors that contribute to the modulation of the vascular tone. Because hemoglobin-based oxygen carriers (HBOC) have been demonstrated to cause vasoconstriction and thereby increase arterial pressure by interacting with endothelium-derived factors such as nitric oxide and endothelin-1, we hypothesized that hemoglobin could penetrate into the endothelial cells. Therefore, we investigated the presence of hemoglobin into guinea pig aortic endothelial cells by immunohistochemical staining after exchange transfusion with a hemoglobin-based oxygen carrier. Despite the large molecular size of HBOC due to chemical modifications designed to prevent hemoglobin subunit dissociation and extravascular leakage, hemoglobin was detectable by immunohistochemical staining into the endothelial cells. These findings suggest that the vascular endothelial cells could uptake hemoglobin by endocytosis mechanisms or could help hemoglobin to cross the endothelial barrier toward media by transcytosis mechanisms. These findings are very important to lead future investigations to the mechanisms by which HBOC cause vasoconstriction.
Blood yield stress in systemic sclerosis
Authors: Picart Catherine , Carpentier Patrick H. , Galliard Hélène , Piau Jean-Michel
Published: December 2017

Blood is a weak percolating physical gel at low shear rates, in which clusters of aggregates can be reversibly disaggregated or formed again. This phenomenon is of potential importance in the microvascular pathophysiology of ischemic and vasospastic disorders such as systemic sclerosis. The aim of this work was to determine blood yield stress using low-shear-rate rheometry with a homemade roughened Couette device in 10 patients with systemic sclerosis compared with 10 healthy controls. Biochemical plasmatic parameters were assessed independently. Results showed a significantly increased stress (+56%, P < 0.05 at 60% hematocrit) for scleroderma patients. The best biochemical predictor for yield stress was the ratio of albumin to globulins; 69% of its variance was explained by plasmatic factors (albumin, fibrinogen, and globulins) in scleroderma patients and 23.4% in healthy controls. Additional microscopic observations showed different microstructures. These results support the hypothesis of an abnormal red blood cell organization process in scleroderma patients that could be partly responsible for the severity of ischemic complications of the disease.
Interstitial Ca2+undergoes dynamic changes sufficient to stimulate nerve-dependent Ca2+-induced relaxation
Authors: Mupanomunda Maria M. , Ishioka Norio , Bukoski Richard D.
Published: December 2017

We recently described a perivascular sensory nerve-linked dilator system that can be activated by interstitial Ca2+([Formula: see text]). The present study tested the hypothesis that [Formula: see text] in the rat duodenal submucosa varies through a range that is sufficient to activate this pathway. An in situ microdialysis method was used to estimate [Formula: see text]. When the duodenal lumen was perfused with Ca2+-free buffer, [Formula: see text] was 1.0 ± 0.13 mmol/l. [Formula: see text] increased to 1.52 ± 0.04, 1.78 ± 0.10, and 1.89 ± 0.1 when the lumen was perfused with buffer containing 3, 6, and 10 mmol/l Ca2+, respectively ( P < 0.05).[Formula: see text] was 1.1 ± 0.06 mmol/l in fasted animals and increased to 1.4 ± 0.06 mmol/l in free-feeding rats ( P < 0.05). Wire myography was used to study isometric tension responses of isolated mesenteric resistance arteries. Cumulative addition of extracellular Ca2+-relaxed serotonin- and methoxamine-precontracted arteries with half-maximal effective doses of 1.54 ± 0.05 and 1.67 ± 0.08 mmol/l, respectively ( n = 5). These data show that duodenal[Formula: see text] undergoes dynamic changes over a range that activates the sensory nerve-linked dilator system and indicate that this system can link changes in local Ca2+transport with alterations in regional resistance and organ blood flow.
α1-Adrenergic stimulation of FGF-2 promoter in cardiac myocytes and in adult transgenic mouse hearts
Authors: Detillieux Karen A. , Meij Johanna T. A. , Kardami Elissavet , Cattini Peter A.
Published: December 2017

Fibroblast growth factor (FGF-2), a mitogenic, angiogenic, and cardioprotective agent, is reported to be released from the postnatal heart by a mechanism of transient remodeling of the sarcolemma during contraction. This release can be increased with adrenergic stimulation. RNA blotting was used to assess whether FGF-2 synthesis in neonatal rat cardiomyocytes might also be regulated by adrenergic stimulation. FGF-2 RNA levels were increased after treatment with norepinephrine for 6 h or with the α-adrenergic agonist phenylephrine for 48 h. To assess an effect on transcription, neonatal rat cardiomyocytes were transfected with a hybrid rat FGF-2 promoter/luciferase gene (−1058FGFp. luc) and treated with norepinephrine or phenylephrine for 6 or 48 h, respectively. FGF-2 promoter activity was increased two- to sevenfold in an α1-specific manner. Putative phenylephrine-responsive elements (PEREs) were identified at positions −780 and −761 relative to a major transcription initiation site. However, deletion analysis of −1058FGFp. luc showed that the phenylephrine response was independent of the putative PEREs, cell contraction, and Ca2+influx. In transgenic mice expressing −1058FGFp. luc, a significant three- to sevenfold stimulation of FGF-2 promoter activity was detected in the hearts of two independent lines 6 h after intraperitoneal administration of phenylephrine (50 mg/kg). This increase was still apparent at 24 h but was not detected at 48 h posttreatment. Analysis of FGF-2 mRNA in normal mouse hearts revealed accumulation of the 6.1-kb transcript at 24 h. Control of local FGF-2 synthesis at the transcriptional level through adrenergic stimulation may be important in the response to injury as well as in the maintenance of a healthy myocardium.
Neutrophils sense flow-generated stress and direct their migration through αVβ3-integrin
Authors: Rainger G. E. , Buckley C. D. , Simmons D. L. , Nash G. B.
Published: December 2017

During inflammation neutrophils are recruited from the blood onto the surface of microvascular endothelial cells. In this milieu the presence of soluble chemotactic gradients is disallowed by blood flow. However, directional cues are still required for neutrophils to migrate to the junctions of endothelial cells where extravasation occurs. Shear forces generated by flowing blood provide a potential alternative guide. In our flow-based adhesion assay neutrophils preferentially migrated in the direction of flow when activated after attachment to platelet monolayers. Neutralizing αVβ3-integrin with monoclonal antibodies or turning the flow off randomized the direction of migration without affecting migration velocity. Purified, immobilized αVβ3-integrin ligands, CD31 and fibronectin, could both support flow-directed neutrophil migration in a concentration-dependent manner. Migration could be randomized by neutralizing αVβ3-integrin interactions with the substrate using antibodies or Arg-Gly-Asp-containing peptide. These results exemplify mechanical signal transduction through integrin-ligand interactions and reveal a guidance system that was hitherto unknown in neutrophils. In more general terms, it demonstrates that cells can use integrin molecules to “sample” their physical microenvironment through adhesion and use this information to modulate their behavior.
Formation of 4-hydroxy-2-nonenal-modified proteins in ischemic rat heart
Authors: Eaton Philip , Li Jian-Mei , Hearse David J. , Shattock Michael J.
Published: December 2017

4-Hydroxy-2-nonenal (HNE) is a major lipid peroxidation product formed during oxidative stress. Because of its reactivity with nucleophilic compounds, particularly metabolites and proteins containing thiol groups, HNE is cytotoxic. The aim of this study was to assess the extent and time course for the formation of HNE-modified proteins during ischemia and ischemia plus reperfusion in isolated rat hearts. With an antibody to HNE-Cys/His/Lys and densitometry of Western blots, we quantified the amount of HNE-protein adduct in the heart. By taking biopsies from single hearts ( n = 5) at various times (0, 5, 10, 15, 20, 35, and 40 min) after onset of zero-flow global ischemia, we showed a progressive, time-dependent increase (which peaked after 30 min) in HNE-mediated modification of a discrete number of proteins. In studies with individual hearts ( n = 4/group), control aerobic perfusion (70 min) resulted in a very low level (296 arbitrary units) of HNE-protein adduct formation; by contrast, after 30-min ischemia HNE-adduct content increased by >50-fold (15,356 units, P < 0.05). In other studies ( n = 4/group), administration of N-(2-mercaptopropionyl)glycine (MPG, 1 mM) to the heart for 5 min immediately before 30-min ischemia reduced HNE-protein adduct formation during ischemia by ∼75%. In studies ( n = 4/group) that included reperfusion of hearts after 5, 10, 15, or 30 min of ischemia, there was no further increase in the extent of HNE-protein adduct formation over that seen with ischemia alone. Similarly, in experiments with MPG, reperfusion did not significantly influence the tissue content of HNE-protein adduct. Western immunoblot results were confirmed in studies using in situ immunofluorescent localization of HNE-protein in cryosections. In conclusion, ischemia causes a major increase in HNE-protein adduct that would be expected to reflect a toxic sequence of events that might act to compromise tissue survival during ischemia and recovery on reperfusion.
Role of nitric oxide-derived oxidants in vascular injury from carbon monoxide in the rat
Authors: Thom Stephen R. , Fisher Donald , Xu Y. Anne , Garner Sarah , Ischiropoulos Harry
Published: December 2017

Studies were conducted with rats to investigate whether exposure to CO at concentrations frequently found in the environment caused nitric oxide (NO)-mediated vessel wall changes. Exposure to CO at concentrations of 50 parts per million or higher for 1 h increased the concentration of nitrotyrosine in the aorta. Immunologically reactive nitrotyrosine was localized in a discrete fashion along the endothelial lining, and this was inhibited by pretreatment with the NO synthase (NOS) inhibitor N ω-nitro-l-arginine methyl ester (l-NAME). The CO-induced elevations of aortic nitrotyrosine were not altered by neutropenia or thrombocytopenia, and CO caused no change in the concentration of endothelial NOS. Consequences from NO-derived stress on the vasculature included an enhanced transcapillary efflux of albumin within the first 3 h after CO exposure and leukocyte sequestration that became apparent 18 h after CO exposure. Oxidized plasma low-density lipoprotein was found immediately after CO exposure, but this was not inhibited byl-NAME pretreatment. We conclude that exposure to relatively low CO concentrations can alter vascular status by several mechanisms and that many changes are linked to NO-derived oxidants.
Beneficial effect of myocardial angiogenesis on cardiac remodeling process by amlodipine and MCI-154
Authors: Kumamoto Hideki , Okamoto Hiroshi , Watanabe Masashi , Onozuka Hisao , Yoneya Keiji , Nakagawa Izumi , Chiba Satoru , Watanabe Satoshi , Mikami Taisei , Abe Kazuhiro , Kitabatake Akira
Published: December 2017

The present study examined the effect of long-term treatment with amlodipine and MCI-154 (a Ca2+ sensitizer) on progressive cardiac dysfunction and microvasculature in the dilated cardiomyopathic (DCM) hamster heart. After treatment of DCM hamsters (Bio 53.58) with amlodipine or MCI-154 for 15 wk from the age of 5 wk, amlodipine and MCI-154 were found to cause an increase in left ventricular percent fractional shortening and decreases in left ventricular diastolic dimension and isovolumic relaxation time in echocardiograms ( P < 0.01). A hemodynamic study showed that the diastolic time constant decreased in the amlodipine-treatment group ( P < 0.05). In a morphometric study employing a double-staining method that discriminated arteriolar and venular capillaries, amlodipine and MCI-154 caused increases in total capillary density ( P < 0.05) and the proportion of venular capillaries ( P < 0.05). Moreover, Northern blot analysis showed that the expression of mRNA for vascular endothelial growth factor was significantly increased by amlodipine and MCI-154. They preserve coronary microvasculature in the DCM hamster and might induce angiogenesis of small vessels, thereby contributing to preservation of cardiac systolic and diastolic function.
Localization and quantitation of cardiac annexins II, V, and VI in hypertensive guinea pigs
Authors: Trouvé Pascal , Legot Sarah , Bélikova Ioulia , Marotte Françoise , Bénévolensky Dmitri , Russo-Marie Françoise , Samuel Jane-Lyse , Charlemagne Danièle
Published: December 2017

Annexins are characterized by Ca2+-dependent binding to phospholipids. Annexin II mainly participates in cell-cell adhesion and signal transduction, whereas annexins V and VI also seem to regulate intracellular calcium cycling. Their abundance and localization were determined in left ventricle (LV) and right ventricle (RV) from hypertensive guinea pigs, during the transition from compensatory hypertrophy to heart failure. Immunoblot analysis of annexins II, V, and VI revealed an increased accumulation (2.6-, 1.45-, and 2.3-fold, respectively) in LV from hypertensive guinea pigs and no modification in RV. Immunofluorescent labeling of annexins II, V, and VI; of Na+-K+-ATPase; and of sarcomeric α-actinin showed that in control LV and RV, 1) annexin II is present in nonmuscle cells; 2) annexins V and VI are mainly observed in the sarcolemma and intercalated disks of myocytes; 3) annexins II, V, and VI strongly label endothelial cells and adventitia of coronary arteries; and 4) annexin VI is present in the media. At the onset of heart failure, the most striking changes are the increased protein accumulation in LV and the very strong labeling of annexins II, V, and VI in interstitial tissue, suggesting a role in fibrosis development and cardiac remodeling.
BAY K 8644 modifies Ca2+cross signaling between DHP and ryanodine receptors in rat ventricular myocytes
Authors: Adachi-Akahane Satomi , Cleemann Lars , Morad Martin
Published: December 2017

The amplification factor of dihydropyridine (DHP)/ryanodine receptors was defined as the amount of Ca2+released from the sarcoplasmic reticulum (SR) relative to the influx of Ca2+through L-type Ca2+channels in rat ventricular myocytes. The amplification factor showed steep voltage dependence at potentials negative to −10 mV but was less dependent on voltage at potentials positive to this value. In cells dialyzed with 0.2 mM cAMP in addition to 2 mM fura 2, the Ca2+-channel agonist (−)-BAY K 8644 enhanced Ca2+-channel current ( ICa), shifted the activation curve by −10 mV, and significantly delayed its inactivation. Surprisingly, BAY K 8644 reduced the amplification factor by 50% at all potentials, even though the caffeine-releasable Ca2+stores were mostly intact at holding potentials of −90 mV. In contrast, brief elevation of extracellular Ca2+activity from 2 to 10 mM enhanced both ICaand intracellular Ca2+transients in the absence or presence of BAY K 8644 but had no significant effect on the amplification factor. BAY K 8644 abolished the direct dependence of the rate of inactivation of ICaon the release of Ca2+from the SR. These findings suggest that the gain of the Ca2+-induced Ca2+release in cardiac myocytes is regulated by the gating kinetics of cardiac L-type Ca2+channels via local exchange of Ca2+signals between DHP and ryanodine receptors and that BAY K 8644 suppresses the amplification factor through attenuation of the Ca2+-dependent inactivation of Ca2+channels.
Two populations of sympathetic neurons project selectively to mesenteric artery or vein
Authors: Browning Kirsteen N. , Zheng Zhongling , Kreulen David L. , Travagli R. Alberto
Published: December 2017

The objective of this study was to determine whether sympathetic neurons of the inferior mesenteric ganglion (IMG) projecting to mesenteric arteries could be distinguished by their localization, neurochemical phenotype, and electrophysiological properties from neurons projecting to mesenteric veins. In an in vitro intact vasculature-IMG preparation, neurons were labeled following intraluminal injection of Fluoro-Gold or rhodamine beads into the inferior mesenteric artery (IMA) or vein (IMV). The somata of neurons projecting to IMA were localized in the central part of the IMG, whereas those projecting to IMV were localized more peripherally. None of the labeled neurons was doubly labeled. Neuropeptide Y immunoreactivity was found in 18.9% of neurons innervating the IMA, but not in neurons innervating the IMV. Identified neurons were dissociated and characterized using whole cell patch-clamp recording. After direct soma depolarization, all of the labeled arterial and venous neurons were classified as tonic firing, compared with only 40% of unlabeled neurons; the remaining 60% of unlabeled neurons were phasic firing. The results indicate that IMG neurons projecting to mesenteric arteries are distinct from neurons projecting to mesenteric veins.
Effects of AT1-receptor blockade on progression of left ventricular dysfunction in dogs with heart failure
Authors: Tanimura Mitsuhiro , Sharov Victor G. , Shimoyama Hisashi , Mishima Takayuki , Levine T. Barry , Goldstein Sidney , Sabbah Hani N.
Published: December 2017

The objective of the present study was to determine the effects of early long-term monotherapy with the angiotensin II AT1-receptor antagonist valsartan on the progression of left ventricular (LV) dysfunction and remodeling in dogs with moderate heart failure (HF). Studies were performed in 30 dogs with moderate HF produced by multiple sequential intracoronary microembolizations. Embolizations were discontinued when LV ejection fraction was 30–40%. Two weeks after the last embolization, dogs were randomized to 3 mo of oral therapy with low-dose valsartan (400 mg twice daily, n = 10), to high-dose valsartan (800 mg twice daily, n = 10), or to no treatment at all (control, n = 10). Treatment with valsartan significantly reduced mean aortic pressure and LV end-diastolic pressure compared with control. In untreated dogs, LV ejection fraction decreased (37 ± 1 vs. 29 ± 1%, P = 0.001) and end-systolic volume (ESV) and end-diastolic volume (EDV) increased (81 ± 5 vs. 92 ± 5 ml, P < 0.001; 51 ± 3 vs. 65 ± 3 ml, P = 0.001, respectively) after 3 mo of follow-up compared with those levels before follow-up. In dogs treated for 3 mo with low-dose valsartan, ejection fraction was preserved (37 ± 1 vs. 38 ± 2%, pretreatment vs. posttreatment) as was ESV but not EDV. In dogs treated for 3 mo with high-dose valsartan, ejection fraction decreased (35 ± 1 vs. 31 ± 2%, P = 0.02) and ESV and EDV increased in a manner comparable to those levels in controls. Valsartan had no significant effects on cardiomyocyte hypertrophy or on the extent of interstitial fibrosis. We conclude that, for dogs with moderate HF, early long-term therapy with the AT1-receptor blocker valsartan decreases preload and afterload but has only limited benefits in attenuating the progression of LV dysfunction and chamber remodeling.
Mechanical properties of mesenteric arteries in diabetic rats: consequences of outward remodeling
Authors: Crijns Francy R. L. , Wolffenbuttel Bruce H. R. , de Mey Jo G. R. , Boudier Harry A. J. Struijker
Published: December 2017

Diabetes induces hemodynamic and biochemical changes that can influence mechanical properties of arteries. Structure and mechanics of mesenteric small arteries were investigated in rats with streptozotocin-induced diabetes (duration 7–9 wk). The external diameter of mesenteric artery branches was measured in control ( n = 9) and diabetic ( n = 7) Wistar Rp rats at baseline and during pressurization in situ (0–150 mmHg) under normal and passive smooth muscle conditions. Mean arterial pressure and mesenteric artery pressure were not significantly different. Baseline mesenteric artery diameter was larger in the diabetes-induced group (439 ± 12 vs. 388 ± 18 μm, P< 0.05). Media cross-sectional area of arteries from diabetic rats was not significantly increased (0.0149 ± 0.0015 vs. 0.0122 ± 0.0007 mm2). Cross-sectional compliance was significantly increased in diabetic rats at intraluminal pressures ranging from 25 to 75 mmHg ( P < 0.005), whereas cross-sectional distensibility was not modified. Wall tension and circumferential wall stress were increased in diabetes. These results indicate that mesenteric small arteries of diabetic rats display eutrophic outward remodeling associated with increased wall tension and circumferential wall stress.
Peroxynitrite contributes to spontaneous loss of cardiac efficiency in isolated working rat hearts
Authors: Ferdinandy Peter , Panas Donna , Schulz Richard
Published: December 2017

We examined the mechanism of the time- and protein synthesis-dependent decline in cardiac mechanical function in isolated working rat hearts. Hearts were perfused with Krebs-Henseleit buffer for 120 min in the presence or absence of the protein synthesis inhibitor cycloheximide (CX; 10 μM). Cardiac work remained stable for 60 min and then spontaneously decreased during 60–120 min of perfusion. This was accompanied by an increase in myocardial inducible nitric oxide synthase (iNOS) and xanthine oxidase (XO) activities and enhanced dityrosine formation in the perfusate, an indicator of peroxynitrite generation. CX markedly attenuated the loss in contractile function and prevented the increase in iNOS and XO activities and dityrosine level. Despite the decline in cardiac work in control hearts, the coupling between tricarboxylic acid (TCA) cycle activity and oxygen consumption remained constant in both groups. ATP, creatine phosphate, and glycogen levels were not different between control and CX groups and did not differ over 120 min of perfusion. We concluded that the delayed and spontaneous loss in myocardial mechanical function in isolated working rat hearts is 1) attenuated by CX treatment, 2) accompanied by a concomitant increase in both iNOS and XO activities and peroxynitrite generation in the heart, and 3) not dependent on a direct impairment in myocardial ATP production, myocardial oxygen consumption, or TCA cycle acetyl-CoA production but may be due to an inefficiency of the heart to utilize ATP for contractile work.
5-(N-ethylcarboxamido)adenosine desensitizes the A2b-adenosine receptor in lung circulation
Authors: Haynes Johnson , Obiako Boniface , Babal Pavel , Stevens Troy
Published: December 2017

The adenosine agonist 5-( N-ethylcarboxamido)adenosine (NECA) induces vasodilation in the pulmonary circulation via A2-adenosine-receptor activation. We addressed whether prolonged treatment with NECA desensitizes in A2-adenosine- receptor function in isolated lung and pulmonary artery smooth muscle cells (PASMC). In lung microcirculation preconstricted with a hypoxic gas, initial administration of NECA caused a 57% vasodilatory response after 3–4 min. Readministration of NECA after 45 min resulted in minimal vasodilation. The highest accumulation of PASMC cAMP occurred 3–5 min after NECA, coincident with NECA-induced vasodilation. In PASMCs treated with NECA for 45 min, cAMP did not increase. Isoproterenol- and indolidan-induced vasodilation remained intact in NECA-desensitized lungs. In NECA-desensitized PASMCs, isoproterenol-induced cAMP accumulation was decreased, suggesting a common mechanism of desensitization. cAMP accumulation was decreased in cholera toxin-treated NECA-desensitized PASMCs compared with cholera toxin-treated control PASMCs, demonstrating that Gsα-adenylyl cyclase signaling contributes to desensitization. The A2a-adenosine-receptor agonist CGS-21680C neither increased cAMP accumulation in PASMCs nor attenuated NECA-induced vasodilation. These data support that the A2b-adenosine receptor is responsible for pulmonary vasodilation and desensitization through mechanisms(s) involving Gsα-adenylyl cyclase signaling.