bluuebunny/crossref_metadata_2025 huggingface dataset:
Stimulation of the Stress-Activated Mitogen-Activated Protein Kinase Subfamilies in Perfused Heart
Authors: Bogoyevitch Marie A. , Gillespie-Brown Judith , Ketterman Albert J. , Fuller Stephen J. , Ben-Levy Rachel , Ashworth Alan , Marshall Christopher J. , Sugden Peter H.
Published: June 2012

It has recently been recognized that cellular stresses activate certain members of the mitogen-activated protein kinase (MAPK) superfamily. One role of these “stress-activated” MAPKs is to increase the transactivating activity of the transcription factors c-Jun, Elk1, and ATF2. These findings may be particularly relevant to hearts that have been exposed to pathological stresses. Using the isolated perfused rat heart, we show that global ischemia does not activate the 42- and 44-kD extracellular signal–regulated (protein) kinase (ERK) subfamily of MAPKs but rather stimulates a 38-kD activator of MAPK-activated protein kinase-2 (MAPKAPK2). This activation is maintained during reperfusion. The molecular characteristics of this protein kinase suggest that it is a member of the p38/reactivating kinase (RK) group of stress-activated MAPKs. In contrast, stress-activated MAPKs of the c-Jun N-terminal kinase (JNK/SAPKs) subfamily are not activated by ischemia alone but are activated by reperfusion following ischemia. Furthermore, transfection of ventricular myocytes with activated protein kinases (MEKK1 and SEK1) that may be involved in the upstream activation of JNK/SAPKs induces increases in myocyte size and transcriptional changes typical of the hypertrophic response. We speculate that activation of multiple parallel MAPK pathways may be important in the responses of hearts to cellular stresses.
Simulation of Action Potentials From Metabolically Impaired Cardiac Myocytes
Authors: Ferrero José M. , Sáiz Javier , Ferrero José M. , Thakor Nitish V.
Published: June 2012

The role of the ATP-sensitive K
+
current (I
K-ATP
) and its contribution to electrophysiological changes that occur during metabolic impairment in cardiac ventricular myocytes is still being discussed. The aim of this work was to quantitatively study this issue by using computer modeling. A model of I
K-ATP
is formulated and incorporated into the Luo-Rudy ionic model of the ventricular action potential. Action potentials under different degrees of activation of I
K-ATP
are simulated. Our results show that in normal ionic concentrations, only ≈0.6% of the K
ATP
channels, when open, should account for a 50% reduction in action potential duration. However, increased levels of intracellular Mg
2+
counteract this shortening. Under conditions of high [K
+
]
o
, such as those found in early ischemia, the activation of only ≈0.4% of the K
ATP
channels could account for a 50% reduction in action potential duration. Thus, our results suggest that opening of I
K-ATP
channels should play a significant role in action potential shortening during hypoxic/ischemic episodes, with the fraction of open channels involved being very low (<1%). However, the results of the model suggest that activation of I
K-ATP
alone does not quantitatively account for the observed K
+
efflux in metabolically impaired cardiac myocytes. Mechanisms other than K
ATP
channel activation should be responsible for a significant part of the K
+
efflux measured in hypoxic/ischemic situations.
MAP Kinase Activation by Flow in Endothelial Cells
Authors: Ishida Takafumi , Peterson Timothy E. , Kovach Nicholas L. , Berk Bradford C.
Published: June 2012

Local alterations in the hemodynamic environment regulate endothelial cell function, but the signal-transduction mechanisms involved in this process remain unclear. We previously demonstrated that mitogen-activated protein (MAP) kinase is rapidly stimulated by flow in bovine aortic endothelial cells. Integrin receptors may act as mechanotransducers, as suggested by rapid remodeling of focal adhesion complexes in response to flow. To study the role of integrins in flow-mediated MAP kinase activation, we compared the effects of β1 integrin activation (with 8A2 antibody) and flow in cultured human umbilical vein endothelial cells (HUVECs). Both 8A2 (3 μg/mL) and flow (shear stress, 12 dynes/cm
2
) stimulated MAP kinase, although the flow response was faster and greater. To characterize flow-activated tyrosine kinases, tyrosine-phosphorylated proteins were immunoprecipitated and identified by Western blot. There was a time-dependent increase in phosphotyrosine content in 60- to 80-kD, 110-kD, 125- to 150-kD, and 180- to 190-kD proteins. A 125-kD protein was identified as focal adhesion kinase (FAK), suggesting that flow activates integrins. In comparison with flow, 8A2 caused less tyrosine phosphorylation of fewer proteins, although FAK was tyrosine phosphorylated. Concurrent stimulation of HUVECs with 8A2 and flow caused additive increases in MAP kinase. Antibody 8A2 increased binding of the β1 affinity–sensitive antibody, 15/7, while flow failed to increase binding of 15/7. In summary, both a β1-activating antibody and flow stimulate tyrosine kinases, leading to activation of FAK and MAP kinase signal-transduction pathways. However, the cellular responses elicited by 8A2 represent only a portion of those stimulated by flow, suggesting that “costimulatory” events such as calcium mobilization, in addition to integrin activation, mediate the HUVEC response to fluid shear stress.
Thyroid Hormone Represses Protein Kinase C Isoform Expression and Activity in Rat Cardiac Myocytes
Authors: Rybin Vitalyi , Steinberg Susan F.
Published: June 2012

We have previously demonstrated that at least four isoforms of protein kinase C (PKC; α, δ, ε, and ζ) are expressed in neonatal rat ventricular myocytes and that development is associated with a decline in their expression. The mechanism(s) regulating PKC isoform expression in ventricular myocytes is completely unknown. The developmental decline in PKC expression occurs, in large part, during the first 2 weeks of postnatal life, while thyroid hormone levels are known to be progressively increasing. Accordingly, this study examined the influence of thyroid hormone on PKC isoform expression to determine whether thyroid hormone can be implicated as a potential physiological regulator of PKC gene expression during normal cardiac development. Hypothyroidism was induced in adult rats by surgical thyroidectomy; thyroid status was manipulated in cultured neonatal ventricular myocytes by growth in serum-free medium with varying triiodothyronine (T
3
) levels. In each case, hypothyroidism was verified by a 10- to 50-fold increase in steady state mRNA for β-myosin heavy chain. In hypothyroid adult ventricular myocardium, there was a selective 60% increase in the expression of PKCε protein that corresponded to an increase in maximally stimulated PKC enzyme activity with PKCε substrate peptide (ε
pep
) but not with histone as substrate. Northern blot analysis revealed a 70% increase in PKCε mRNA, indicating that the regulatory effects of thyroid hormone are mediated, at least in part, at the message level. In neonatal ventricular myocytes, there was a T
3
-dependent reduction in immunoreactivity for both PKCα and PKCε that was associated with significant reductions in both histone- and ε
pep
-kinase activities. The concentration of T
3
that half-maximally repressed PKCα and PKCε expression was ≈0.5 nmol/L. Thyroid hormone had no effect on PKCδ and PKCζ expression in neonatal or adult ventricular myocytes. PKC isoform expression in cardiac fibroblasts was not influenced by variations in the thyroid hormone concentration during culture. These results provide evidence that thyroid hormone specifically represses PKCα and PKCε in the neonatal heart and PKCε in the adult heart. Thyroid hormone–induced changes in PKC may play an important permissive role in the modulation of autonomic responsiveness in ventricular cardiomyocytes.
The Electrophysiological Mechanism of Ventricular Arrhythmias in the Long QT Syndrome
Authors: El-Sherif Nabil , Caref Edward B. , Yin Hong , Restivo Mark
Published: June 2012

We have previously developed a canine in vivo model of the long QT syndrome (LQTS) using the neurotoxin anthopleurin A (AP-A), which acts by slowing sodium channel inactivation. The recent discovery of a genetic mutation in the cardiac sodium channel in some patients with the congenital LQTS, resulting in abnormal gating behavior similar to sodium channels exposed to AP-A, provides a strong endorsement of this animal model as a valid surrogate to the clinical syndrome of LQTS. In the present study, we conducted high-resolution tridimensional isochronal mapping of both activation and repolarization patterns in puppies exposed to AP-A that developed LQTS and polymorphic ventricular tachyarrhythmias (VTs). To map repolarization, we measured activation-recovery intervals (ARIs) using multiple unipolar extracellular electrograms. We demonstrated, for the first time in vivo, the existence of spatial dispersion of repolarization in the ventricular wall and differences in regional recovery in response to cycle-length changes that were markedly exaggerated after AP-A administration. Analysis of tridimensional activation patterns showed that the initial beat of polymorphic VT consistently arose as focal activity from a subendocardial site, whereas subsequent beats were due to successive subendocardial focal activity, reentrant excitation, or a combination of both mechanisms. Reentrant excitation was due to infringement of a focal activity on the spatial dispersion of repolarization, resulting in functional conduction block and circulating wave fronts. The polymorphic QRS configuration of VT in the LQTS was due to either changing the site of origin of focal activity, resulting in varying activation patterns, or varying orientations of circulating wave fronts.
Cloning and Characterization of Rat Density-Enhanced Phosphatase-1, a Protein Tyrosine Phosphatase Expressed by Vascular Cells
Authors: Borges Luis G. , Seifert Ronald A. , Grant Francis J. , Hart Charles E. , Disteche Christine M. , Edelhoff Susanne , Solca Flavio F. , Lieberman Michael A. , Lindner Volkhard , Fischer Edmond H. , Lok Si , Bowen-Pope Daniel F.
Published: June 2012

We have cloned from cultured vascular smooth muscle cells a protein tyrosine phosphatase, rat density-enhanced phosphatase-1 (rDEP-1), which is a probable rat homologue of DEP-1/HPTPη. rDEP-1 is encoded by an 8.7-kb transcript and is expressed as a 180- to 220-kD protein. The rDEP-1 gene is located on human chromosome 11 (region p11.2) and on mouse chromosome 2 (region 2E). The cDNA sequence predicts a transmembrane protein consisting of a single phosphatase catalytic domain in the intracellular region, a single transmembrane domain, and eight fibronectin type III repeats in the extracellular region (GenBank accession number
U40790
). In situ hybridization analysis demonstrates that rDEP-1 is widely expressed in vivo but that expression is highest in cells that form epithelioid monolayers. In cultured cells with epitheliod morphology, including endothelial cells and newborn smooth muscle cells, but not in fibroblast-like cells, rDEP-1 transcript levels are dramatically upregulated as population density increases. In vivo, quiescent endothelial cells in normal arteries express relatively high levels of rDEP-1. During repair of vascular injury, expression of rDEP-1 is downregulated in migrating and proliferating endothelial cells. In vivo, rDEP-1 transcript levels are present in very high levels in megakaryocytes, and circulating platelets have high levels of the rDEP-1 protein. In vitro, initiation of differentiation of the human megakaryoblastic cell line CHRF-288-11 with phorbol 12-myristate 13-acetate leads to a very strong upregulation of rDEP-1 transcripts. The deduced structure and the regulation of expression of rDEP-1 suggest that it may play a role in adhesion and/or signaling events involving cell-cell and cell-matrix contact.
Biochemical and Pharmacological Properties of SANORG 32701
Authors: Herbert J.M. , He´rault J.P. , Bernat A. , van Amsterdam R.G.M. , Vogel G.M.T. , Lormeau J.C. , Petitou M. , Meuleman D.G.
Published: June 2012

SANORG 32701 is a new sulfated pentasaccharide obtained by total chemical synthesis. It is an analogue of the “synthetic pentasaccharide” (SR 90107/ORG 31540), which represents the antithrombin III (AT-III) binding site of heparin. Like SR 90107, it shows high affinity for human AT-III (
K
d
=3.7±0.7 nmol/L) and is a potent catalyst of its inhibitory effect with regard to factor Xa (1100±31 versus 850±27 anti-Xa U/mg for SR 90107). SANORG 32701 inhibited thrombin generation occurring via both the extrinsic and intrinsic pathways in vitro. After intravenous or subcutaneous administration to rabbits or rats, SANORG 32701 displayed prolonged anti–factor Xa activity and inhibition of thrombin generation ex vivo. SANORG 32701 was slowly eliminated, showing elimination half-lives between 2.8 and 4.9 hours with different doses. SANORG 32701 displayed antithrombotic activity by virtue of its potentiation of the anti–factor Xa activity of AT-III. It strongly inhibited thrombus formation in an experimental model of thromboplastin-induced venous thrombosis in rats (intravenously) and rabbits (subcutaneously) (ED
50
values were 25.5±4.1 and 91±12.7 nmol/kg, respectively). SANORG 32701 inhibited the accretion of fibrinogen I 125 to a preformed thrombus in the rabbit jugular vein and significantly reduced thrombus growth occurring after electrical stimulation of the rabbit carotid artery. In the rabbit, intravenous injection of SANORG 32701 enhanced tissue plasminogen activator (TPA)–induced thrombolysis, suggesting that concomitant use of SANORG 32701 during TPA therapy may be helpful in preventing thrombus accretion, thus facilitating clot lysis. In the rat, SANORG 32701 potently inhibited thrombus formation induced on a silk thread in an arteriovenous shunt and in the vena cava. Compared with standard heparin, SANORG 32701 (1000 nmol/kg IV) caused only minimal bleeding enhancement and exhibited a favorable antithrombotic activity/bleeding risk ratio, therefore showing that it might be considered as a promising compound in the treatment and prevention of various thrombotic diseases.
Differential Expression of Voltage-Gated K
+
Channel Genes in Left Ventricular Remodeled Myocardium After Experimental Myocardial Infarction
Authors: Gidh-Jain Madhavi , Huang Boyu , Jain Praveer , El-Sherif Nabil
Published: June 2012

Left ventricular (LV) remodeling after experimental myocardial infarction (MI) is associated with hypertrophy of noninfarcted myocardium and electrophysiological alterations. We have recently shown that post-MI hypertrophied LV myocytes have prolonged action potential duration (APD) and generate triggered activity from early afterdepolarizations. The prolonged APD was attributed to decreased density of the two outward K
+
currents, I
to-fast
(I
to-f
) and I
to-slow
(I
to-s
), rather than changes in the density and/or kinetics of the L-type Ca
2+
current. The changes in ionic current density may be related to alterations in the expression and levels of ion channel proteins. To test this hypothesis, rats underwent either left anterior descending coronary artery (LAD) ligation (post-MI group [n=10]) or sham surgery (sham group [n=10]). Three weeks later, transcripts from the noninfarcted LV myocardium in the post-MI group (n=6) and LV myocardium of the sham group (n=6) were analyzed by RNase protection assay. Expressions of five K
+
channel subunit mRNAs (Kv1.2, Kv1.4, Kv1.5, Kv2.1, and Kv4.2) reported in the rat ventricle were analyzed. Compared with the sham group, expressions of Kv1.4, Kv2.1 (putative I
to-s
), and Kv4.2 (putative I
to-f
) channel subunit mRNAs were significantly decreased by 60% (
P
<.03), 54% (
P
<.005), and 53% (
P
<.002), respectively, in the post-MI group. There was no significant change in the Kv1.2 and Kv1.5 mRNA levels. Western blotting demonstrated a similar decrease in the Kv2.1 and Kv4.2 immunoreactive protein levels (43% [
P
<.03] and 67% [
P
<.003], respectively [n=4]) and no significant change in Kv1.5 immunoreactive protein level. Our results strongly correlate with the electrophysiological findings in this model and show that transcriptional regulation in the post-MI remodeled rat LV is distinct for each voltage-gated K
+
channel subunit. These findings provide, at least in part, the molecular basis for the electrophysiological alterations observed in this model.
Effects of Thyroid Hormone on Left Ventricular Performance and Regulation of Contractile and Ca
2+
-Cycling Proteins in the Baboon
Authors: Khoury Saeb F. , Hoit Brian D. , Dave Vrushank , Pawloski-Dahm Corinn M. , Shao Yanfu , Gabel Marjorie , Periasamy Muthu , Walsh Richard A.
Published: June 2012

The transcriptional, posttranscriptional, and related functional effects of thyroid hormone on primate myocardium are poorly understood. Therefore, we studied the effects of thyroid hormone on sarcoplasmic reticulum (SR) Ca
2+
-cycling proteins and myosin heavy chain (MHC) composition at the steady state mRNA and protein level and associated alterations of left ventricular (LV) performance in 8 chronically instrumented baboons. The force-frequency and relaxation-frequency relations were assessed as the response of LV isovolumic contraction (dP/dt
max
) and relaxation (Tau), respectively, to incremental atrial pacing. Both the heart rate at which dP/dt
max
was maximal and Tau was minimal (critical heart rates) in response to pacing were increased significantly after thyroid hormone. Postmortem LV tissue from 5 thyroid-treated and 4 additional control baboons was assayed for steady state mRNA levels with cDNA probes to MHC isoforms and SR Ca
2+
-cycling proteins. Steady state SR Ca
2+
-ATPase and phospholamban mRNA increased in the hyperthyroid state, and α-MHC mRNA appeared de novo, whereas β-MHC mRNA decreased. Western analysis (4 thyroid-treated and 4 control baboons) showed directionally similar changes in MHC isoforms and a slight increase in SR Ca
2+
-ATPase. In contrast, there was a statistically nonsignificant decrease in phospholamban protein, which resulted in a significant 40% decrease in the ratio of phospholamban to SR Ca
2+
-ATPase. Thus, thyroid hormone increases the transcription of Ca
2+
-cycling proteins and shifts MHC isoform expression in the primate LV. Our data suggest that both transcriptional and posttranslational mechanisms determine the levels of these proteins in the hyperthyroid primate heart and mediate, in part, the observed enhanced basal and frequency-dependent LV performance.
Mechanical Stretch Induces Enhanced Expression of Angiotensin II Receptor Subtypes in Neonatal Rat Cardiac Myocytes
Authors: Kijima Kazuhisa , Matsubara Hiroaki , Murasawa Satoshi , Maruyama Katsuya , Mori Yasukiyo , Ohkubo Naohiko , Komuro Issei , Yazaki Yoshio , Iwasaka Toshiji , Inada Mitsuo
Published: June 2012

Mechanical stress plays a pivotal role in the development of cardiac hypertrophy during hemodynamic overload, and angiotensin (Ang) II secreted from stretched myocytes plays an important role in mechanical stretch–induced hypertrophy. In the present study, we examined stretch-induced expression of Ang II receptors in an in vitro stretch model using 1-day-old rat myocytes. Both Ang II type 1 receptor (AT1-R) and type 2 receptor (AT2-R) mRNA levels were upregulated by myocyte stretching with similar time courses: significant increases were evident 6 hours after stretching, maximal levels (2.8- and 3.3-fold, respectively) were observed at 12 hours, and these were sustained for up to 18 hours. Ang II receptor expression in fibroblast-rich cultures was not affected by stretching. Conditioned medium in which myocytes were stretched for 12 hours significantly downregulated AT1-R and AT2-R mRNA levels in recipient myocytes, and this effect was almost completely blocked by AT1-R antagonists but not AT2-R antagonists. Stretch-induced expression of AT1-R and AT2-R mRNAs was further increased by 27% and 31%, respectively, after pretreatment with AT1-R antagonists, suggesting that Ang II secreted from stretched myocytes downregulates both AT1-R and AT2-R. Western blot and binding assays showed that the number of AT1-Rs and AT2-Rs increased by 2.4- and 2.6-fold, respectively, without affecting receptor affinities. Inositol phosphate response to 0.5 μmol/L Ang II was enhanced 2.1-fold in stretched myocytes. Nuclear runoff assays and treatment with actinomycin D revealed that stretch-induced upregulation of AT1-R was mainly due to increased transcription, whereas that of AT2-R resulted from a stabilizing effect on AT2-R mRNA metabolism. Stretch-induced changes in levels of Ang II receptors were inhibited by genistein but not by H-7, staurosporin, and protein kinase C depletion or by BAPTA-AM. Exposure to cycloheximide did not affect stretch-induced changes. These findings indicate that nonsecretory pathways activated by myocyte stretching upregulate the expression of Ang II receptor subtypes transcriptionally and posttranscriptionally through mechanisms involving stretch-activated tyrosine kinases independently of de novo protein synthesis and that the AT1-R–mediated action of Ang II is functionally enhanced in stretched cardiac myocytes.
Shock-Induced Depolarization of Refractory Myocardium Prevents Wave-Front Propagation in Defibrillation
Authors: Kwaku Kevin F. , Dillon Stephen M.
Published: June 2012

The elimination of most, if not all, propagating wave fronts of electrical activation by a shock constitutes a minimum prerequisite for successful defibrillation. However, the factors responsible for the prevention of postshock propagating activity are unknown. We investigated the determinants of this effect of defibrillation shocks in 23 Langendorff-perfused rabbit hearts by optically mapping cardiac cellular electrical activity by means of laser scanning. The optical action potentials obtained by this method were continuously recorded from 100 ventricular epicardial sites before, during, and after shock delivery during fibrillation. Analysis of activation maps showed that postshock propagating activity arose from areas depolarized by the shock. In 273 shock episodes, 898 sites at the border of shock-depolarized areas (BSDAs) from which wave-front propagation could have arisen were identified. The incidence of postshock propagation from BSDA sites was inversely related to refractoriness, as indexed by coupling interval (CI) or the optical takeoff potential (V¯
m
). Specifically, there was a near-zero probability of postshock propagation if the shock caused depolarization at CIs <50% of the fibrillation cycle length or from myocardium still depolarized to ≥60% of the amplitude of a paced action potential (APA). Furthermore, incidences of wave-front propagation following shocks were consistently lower than the propagation incidences of naturally occurring unshocked fibrillation wave fronts, at comparable CIs and V¯
m
s. We conclude that the incidence of postshock wave-front propagation decreases with increasing refractoriness at the BSDA and that shock-induced depolarization of effectively refractory myocardium (ie, depolarized to ≥60% APA) is required to guarantee the cessation of continued wave-front propagation in defibrillation.
Phosphorylation of Endothelial Nitric Oxide Synthase in Response to Fluid Shear Stress
Authors: Corson Marshall A. , James Natalie L. , Latta Shawn E. , Nerem Robert M. , Berk Bradford C. , Harrison David G.
Published: June 2012

Endothelial cells release nitric oxide (NO) more potently in response to increased shear stress than to agonists which elevate intracellular free calcium concentration ([Ca
2+
]
i
). To determine mechanistic differences in the regulation of endothelial constitutive NO synthase (ecNOS), we measured NO production by bovine aortic endothelial cells exposed to shear stress in a laminar flow chamber or treated with Ca
2+
ionophores in static culture. The kinetics of cumulative NO production varied strikingly: shear stress (25 dyne/cm
2
) stimulated a biphasic increase over control that was 13-fold at 60 minutes, whereas raising [Ca
2+
]
i
caused a monophasic 6-fold increase. We hypothesized that activation of a protein kinase cascade mediates the early phase of flow-dependent NO production. Immunoprecipitation of ecNOS showed a 210% increase in phosphorylation 1 minute after flow initiation, whereas there was no significant increase after Ca
2+
ionophore treatment. Although ecNOS was not tyrosine-phosphorylated, the early phase of flow-dependent NO production was blocked by genistein, an inhibitor of tyrosine kinases. To determine the Ca
2+
requirement for flow-dependent NO production, we measured [Ca
2+
]
i
with a novel flow-step protocol. [Ca
2+
]
i
increased with the onset of shear stress, but not after a step increase. However, the step increase in shear stress was associated with a potent biphasic increase in NO production rate and ecNOS phosphorylation. These studies demonstrate that shear stress can increase NO production in the absence of increased [Ca
2+
]
i
, and they suggest that phosphorylation of ecNOS may importantly modulate its activity during the imposition of increased shear stress.
Variation in the Velocity, Deformation, and Adhesion Energy Density of Leukocytes Rolling Within Venules
Authors: Damiano E.R. , Westheider J. , Tözeren A. , Ley K.
Published: June 2012

Leukocyte rolling along the endothelium in inflammation is caused by continuous formation and breakage of bonds between selectin adhesion molecules and their ligands. We investigated trauma-induced leukocyte rolling in venules (diameter, 23 to 58 μm; wall shear stress, 1.2 to 35 dyne/cm
2
) of the exteriorized rat mesentery using high-resolution intravital microscopy. While rolling, the leukocytes deformed into a teardroplike shape. Deformation continued to increase with shear stress up to the highest values observed (35 dyne/cm
2
). Successive leukocytes had similar rolling velocities at the same axial positions along each vessel, suggesting that heterogeneity of endothelial adhesiveness is responsible for velocity variation. Adhesion energy density varied inversely with instantaneous rolling velocity and directly with instantaneous deformation. Adhesion energy density reached a maximum of 0.36 dyne/cm, similar to values found for lymphocyte function–associated antigen-1–dependent adhesion of stimulated T cells to isolated intercellular adhesion molecule-1. We conclude that selectin-mediated adhesion during rolling produces adhesion energy densities comparable to those observed for integrin-mediated adhesion events in other experimental systems.
Distinct Phenotype of E-Selectin–Deficient Mice
Authors: Kunkel Eric J. , Ley Klaus
Published: June 2012

Leukocyte capture and rolling are mediated by calcium-dependent lectins expressed on most leukocytes (L-selectin) and the vascular endothelium (P- and E-selectin). To study the role of the selectins during inflammation, we have investigated leukocyte rolling in venules of tumor necrosis factor-α (TNF-α)–treated mouse cremaster muscles in wild-type mice and gene-targeted mice with homozygous deficiency for L-, P-, or E-selectin (L−/−, P−/−, or E−/−, respectively). TNF-α treatment induces expression of E-selectin and increases expression of P-selectin on endothelial cells. Consistent with previous reports of redundant P- and E-selectin function, a combination of monoclonal antibodies (mAbs) against P- and E-selectin (RB40.34 and 9A9, respectively) was necessary to block rolling in wild-type mice. The rolling leukocyte flux fraction (percent rolling cells) in L−/− mice was similar to that in wild-type mice, but rolling in these mice was blocked by a P-selectin mAb. The velocity of rolling leukocytes in TNF-α–treated wild-type, P−/−, or L−/− mice was 5 to 10 times slower (3 to 7 μm/s) than during trauma-induced rolling (20 to 50 μm/s). In contrast, leukocytes in venules of TNF-α–treated E−/− mice rolled significantly faster (12 to 20 μm/s); the rolling leukocyte flux fraction was more than doubled compared with wild-type, L−/−, or P−/− mice; and the number of adherent leukocytes was reduced. Addition of an E-selectin mAb, but not a P-selectin mAb, increased rolling flux fraction and rolling velocity in wild-type mice. Histological analysis revealed that 90% to 95% of all leukocytes interacting (rolling and adherent) with the venular endothelium in TNF-α–treated wild-type, L−/−, P−/−, and E−/− mice were granulocytes. These results identify a previously unrecognized phenotype of E−/− mice by establishing that at the site densities prevailing in vivo, E-selectin is responsible for slow (≈5 μm/s) granulocyte rolling. E-selectin–dependent slow rolling drastically increases the transit time of leukocytes rolling through an inflamed tissue and thus aids in targeting leukocytes activated by chemoattractants to the inflammatory microenvironment.
Studies on the Production of Intravascular Thrombi and Their Treatment with Fibrinolysin
Authors: FREIMAN A. H. , BANG N. U. , CLIFFTON E. E.
Published: June 2012

In 22 dogs, the effect of fibrinolysin therapy of fresh intravascular clots was evaluated by serial angiograms and autopsies. The average time required for dissolution of such clots, when treated by systemic plasmin, was 4 hours and 45 minutes, while the average time necessary for lysis with local fibrinolytic therapy was 2 hours 10 minutes. Treatment of fresh venous and arterial clots did not disclose any significant difference in susceptibility to lysis. In 21 dogs, the effect of age of the clot on the effectiveness of plasmin therapy was studied in clots formed with serum and morrhuate. Clots treated within 4 days of formation were susceptible to dissolution, although clots treated after 3 days did not uniformly undergo complete lysis. The serum-induced clots were more amenable to fibrinolytic therapy than were those formed with morrhuate.
Vascular Muscle Reactivity
Authors: DODD W. ALAN , DANIEL EDWIN E.
Published: June 2012

Arterial contractility was investigated, using spiral and ring sections of dog, cat, rabbit, rat, and human vessels. Epinephrine produced contractions of all arterial tissue tested. Histamine invariably produced contractions. The phenomenon of variable sensitivity of arterial tissue to histamine was again demonstrated. Acetylcholine caused contractions of rabbit, cat, and rat aortas, but no contraction of the dog aorta, or dog and human femoral arteries was observed. Pitressin produced contraction of the rat aorta, and dog and human femoral arteries, but not of rabbit, dog or cat aortas.

Using dog vessels, a difference in activity was observed between the aorta and the femoral artery. Greater reactivity in terms of maximum rate of tension increase and tension developed was seen in the smaller systemic arteries. A pharmacologic difference with respect to the action of pitressin was discovered between the aorta and the smaller arteries. Thus, general evidence is presented suggesting that data obtained in 1 species of animal on 1 type of tissue cannot be transferred without specific proof of its validity to data obtained in other species, or even in closely related tissues of the same species.

An apparent antagonistic effect of pitressin on the pressor action of epinephrine was detected.
Factor Analysis of the Electrocardiogram
Authors: SCHER A. M. , YOUNG A. C. , MEREDITH W. M.
Published: June 2012

The factor analysis of electrocardiograms from 17 normal individuals indicates that over 95 per cent of all the electrocardiographic "information" is accounted for by 3 factors. In the entire series, all individual leads were more than 93 per cent accounted for by 3 factors. These results indicate that there are no significant voltages at the body surface in normal individuals which can be ascribed to more than 3 internal generators. While these results indicate a 3-function system, they do not indicate a dipolar system since a dipole is a special case of a more general 3-function system.
Vascular Effects of Hypertonic Solutions
Authors: READ RAYMOND C. , JOHNSON JOHN A. , VICK JAMES A. , MEYER MAURICE W.
Published: June 2012

During the course of an investigation into the treatment of metabolic acidosis arising from total body perfusion, it was noticed that the intra-arterial administration of concentrated alkalies resulted in a fall in arteriovenous pressure difference at constant flow. A similar decline in peripheral resistance could be produced by hypertonic sugar and salt solutions. This response was found to be independent of the central nervous system. The role of the vasodilatation in the complex vasomotor reaction to the rapid intravenous injection of hyperosmotic agents was then investigated in the intact and vagotomized dog. It was found that when concentrations of up to 1,500 mOsm./L. were used, the predominant response was a delayed hypotension consistent with peripheral vasodilatation. This reaction was complicated by preliminary pulmonary hypertension when solutions containing more than 2,000 mOsm./L. were administered. Twenty per cent NaCl produced such a severe initial phase that the animals frequently died from acute cor pulmonale. The site of obstruction to blood flow through the lungs was variable. Fifty percent glucose could incite pulmonary hypertension, but urea was anomalous in that it was never observed to produce pulmonary vascular effects. Studies in the isolated perfused lung indicated that, again with the exception of urea, all solutions with an osmolarity equal or greater than 5 per cent NaCl evoked pulmonary hypertension. The increase in pulmonary vascular resistance was transitory in spite of recirculation. No response could be elicited when red cells were absent from the perfusate even though, under these conditions, the lung was still sensitive to serotonin. Microscopic examination of the circulation through the brain, lung, mesentery and thigh of both cat and dog demonstrated that intravascular red-cell agglutination occurred after regional arterial injection of highly concentrated salt and sugar solutions. This alteration in the stability of the red-cell stream is considered to be responsible for the obstructive effects of hyperosmotic agents previously attributed to vasospasm.
Volume Pressure Relationships of the Pulmonary-Left Heart Vascular Segment
Authors: LITTLE ROBERT C.
Published: June 2012

Volume-pressure curves were determined for the living left heart vascular segment by injecting fluid into the left atrium during momentary cardiac asystole and measuring left atrial pressure. Such curves show 2 essentially linear relationships with a break at a low pressure level. It has been suggested that this break is due to closure of the pulmonary veins or the pulmonary-left atrial junction at low pressure levels. This closure prevents regurgitation into the pulmonary veins. Higher atrial pressures overcome this block and permit retrograde perfusion of the pulmonary pathways. This suggestion was tested by measuring left atrial and pulmonary vein pressure during the injection of blood into the atrium of the quiescent heart. The results are consistent with such a collapse of the veno-left atrial junction at low pressure levels.
Mechanism of S-T Segment Alteration During Acute Myocardial Injury
Authors: SAMSON WERNER E. , SCHER ALLEN M.
Published: June 2012

Electrocardiograms recorded with a direct-coupled amplifier and recordings of intramyocardial and intracellular potentials were used to determine the nature of the S-T segment shift after myocardial injury. Immediately after coronary artery ligation in the dog, both true S-T and T-Q changes are produced. Lack of responsiveness to the activation wave in the injured area does not account for the initial change in the S-T segment. Changes in the intracellular action potential can be correlated with the electrocardiographic changes. Immediately after injury, cells in the injured area usually repolarize more rapidly than normal cells and this change is significantly correlated with S-T segment shifts. A decrease in resting potential, generally oc curring later than the action potential changes, is similarly correlated with T-Q segment changes.
Electrolyte Changes in Heart Tissue and Coronary Arterial and Venous Plasma Following Coronary Occlusion
Authors: CUMMINGS JOHN R.
Published: June 2012

When coronary sinus and arterial plasma samples obtained during a period of ventricular tachycardia 8 to 11 hours after coronary ligation were analyzed for electrolyte concentrations, it was found that there was an increase in K and Mg and a decrease in Ca and Na. By comparison, when blood samples were taken from sham dogs 8 to 11 hours after the ligatures had simply been placed under the artery, no significant change in plasma cation concentrations over control values was observed. Infarcted ventricular tissue, as compared with noninfarcted tissue, contained an average of 5.1 mEq./100 Gm. wet weight more Na, 4.0 mEq./100 Gm. wet weight less K, and 1.12 mEq./100 Gm. wet weight less Mg.
Investigation of Spontaneous Vasomotor Activity
Authors: CUTHBERTSON ELIZABETH M. , GILFILLAN RUTHERFORD S. , DUINO MIKEL , Bruga Richard D.
Published: June 2012

Spontaneous vasomotor activity, as evidenced by the presence of alpha or beta waves in the paw plethysmogram, was demonstrated in 10 sympathectomized, 4 denervated, and 8 (ganglionic or adrenergic) blockaded extremities in dogs. Alpha waves occur during natural sleep and during anesthesia. They are present after removal and denervation of the carotid and aortic chemoreceptors. They occur in the splenectoinized animal. Alpha waves are usually synchronous in a pair of normally innerverted extremities. They may be synchronous, asynchronous, or absent in one paw when one extremity (or both) is denervated or sympathectomized. The significance of this information is discussed in relation to the factors which may control spontaneous vasomotor activity.
Pericardial and Ventricular Pressure
Authors: HOLT J. P. , RHODE E. A. , KINES HELGA , Ruth Hawkins
Published: June 2012

In anesthetized open-chest and closed-chest dogs subjected to plethora and hemorrhage, pressures were measured simultaneously in the right atrium, right and left ventricles, and the pleural and pericardial spaces. It was found that an increase in ventricular end-diastolic pressure above approximately 1 mm. Hg was associated with a rise in pericardial pressure of nearly the same amount. Thus, the practice of defining "effective" ventricular end-diastolic pressure as the difference between the ventricular and intrapleural pressure gives erroneous values when ventricular end-diastolic pressure is greater than a few mm. Hg. The true ventricular transmural pressure is the difference between ventricular end-diastolic and pericardial end-diastolic pressure and has a value of no more than 2 or 3 mm. Hg under all except the most abnormal circumstances. When ventricular end-diastolic pressure is greater than a few mm. Hg, the pericardial pressure at the end of systole is likewise elevated, but to a lesser degree. Thus, when ventricular end-diastolic pressure is elevated, the measured ventricular end-systolic pressure is greater than the pressure developed by ventricular muscular contraction because end-systolic pressure is the algebraic sum of the pressure developed by ventricular muscular contraction and the pressure in the pericardial space. This error in ventricular systolic pressure may be relatively large for the right and small for the left ventricle. Pericardial pressure decreases during ventricular systole, lowers the pressure on the outside of the atria, and thus, tends to draw blood into the right atrium during ventricular systole.
Intestinal Tissue Blood Flow in Shock Due to Endotoxin
Authors: RAYNER RALPH R. , MacLEAN LLOYD D. , GRIM EUGENE , Levy Louis M.
Published: June 2012

An attempt has been made to measure the capillary blood flows through the individual tissues of the ileum of normal dogs and those which were in endotoxin shock. The technic used was based upon the assumption that the uptake of D
2
O by the tissues was limited by the capillary flow. In loops from endotoxin shock dogs which were perfused at normal blood pressure (135 mm. Hg), the tissue perfusion ratios calculated on this assumption were reduced to about one-half of the control value in the mucosa and to about three-fourths in the submucosa and muscularis, despite the fact that total blood flow was unchanged. When the loops from shock dogs were perfused at the dog's pressure (70 mm. Hg), there was a further decrease of about 50 per cent in both the total blood flow and the tissue perfusion ratios. It is concluded that this reduction in tissue capillary flow, especially in the mucosa, may be the basis of the pathological changes in the intestine in endotoxin shock.
Some Histochemical Observations on the Human Aortic Wall in Atherosclerosis
Authors: SANDLER MAURICE , BOURNE GEOFFREY H.
Published: June 2012

A decrease in the ATPase (heat stable) and 5-nucleotidase of atherosclerotic regions in human aortae has been demonstrated. An increase in the breakdown of TPN, as measured by phosphate release, of the atherosclerotic aorta as a whole has been shown. No change was observed in the breakdown of DPN, as measured by phosphate release, between the normal or atherosclerotic aorta. No reactivity for glucose-1 or glucose-6-phosphate or β-glycerophosphate was found in the intima or media. The possible implications in the development of atheroma are discussed.
Electrophysiologic Effects of Acute Myocardial Ischemia
Authors: Shaw Robin M. , Rudy Yoram
Published: June 2012

A multicellular ventricular fiber model was used to determine mechanisms of slowed conduction and conduction failure during acute ischemia. We simulated the three major pathophysiological component conditions of acute ischemia: elevated [K
+
]
o
, acidosis, and anoxia. Elevated [K
+
]
o
was the major determinant of conduction, causing supernormal conduction, depressed conduction, and conduction block as [K
+
]
o
was gradually increased from 4.5 to 14.4 mmol/L. Only elevated [K
+
]
o
caused conduction failure when varied within the range reported for acute ischemia. Before block, depressed upstrokes consisted of two distinct components: the first to the fast Na
+
current (I
Na
) and the second to the L-type Ca
2+
current (I
Ca(L)
). Even in highly depressed conduction, excitability was maintained by I
Na
, with conduction block occurring at 95% I
Na
inactivation. However, because I
Ca(L)
supported the later phase of the depressed upstroke, I
Ca(L)
enhanced conduction and delayed block by increasing the electrotonic source current. At [K
+
]
o
=18 mmol/L, slow action potentials generated by I
Ca(L)
were obtained with 10% I
Ca(L)
augmentation. However, in the presence of acidosis and anoxia, significantly larger (120%) I
Ca(L)
augmentation was required. The depressant effect was due mostly to anoxic activation of outward ATP-sensitive K
+
current, which counteracts inward I
Ca(L)
and, by lowering the action potential amplitude, decreases the electrotonic current available to depolarize downstream cells. The simulations highlight the interactive nature of electrophysiological ischemic changes during propagation and demonstrate that both membrane changes and load factors (by downstream fiber) must be considered.
In Vitro Modulation of a Resistance Artery Diameter by the Tissue Renin-Angiotensin System of a Large Donor Artery
Authors: Henrion Daniel , Benessiano Joe¨lle , Le´vy Bernard I.
Published: June 2012

A local renin-angiotensin system (RAS) is present in the vasculature and might have an important role in the control of vascular resistance. In order to assess its functional role in the control of vasomotor tone, we investigated the effect of the RAS of a donor vessel (rat carotid artery) on the diameter of a recipient rat mesenteric resistance artery. Arteries were perfused in series in an arteriograph at a rate of 100 μL/min, under a pressure of 100 mm Hg. The two vessels were superfused in separate organ chambers to which drugs were added. Recipient artery internal diameter was measured continuously. Phenylephrine (0.1 μmol/L) was present in the organ baths throughout the experiments, ensuring a preconstriction of the recipient artery (236±4 to 174±3 μm, n=65 arterial segments from 34 rats). The angiotensin I–converting enzyme inhibitors (ACEIs) cilazapril (1 μmol/L) and captopril (10 μmol/L) inhibited phenylephrine-induced constriction by 30±12% (n=7,
P
<.001) and 20±8% (n=5,
P
<.01), respectively. Addition of cilazapril (1 μmol/L) or captopril (10 μmol/L) to the donor vessel chamber further inhibited the constriction by 8±3% (n=7,
P
<.01) and 31±10% (n=5,
P
<.05), respectively. The angiotensin II receptor (AT
1
) antagonist losartan (10 μmol/L) prevented, in part, the relaxation due to the ACEI. The association of losartan (10 μmol/L) with the bradykinin B
2
receptor antagonist HOE 140 (1 μmol/L) totally prevented the relaxation due to the ACEI. Finally, angiotensin II was measured in the perfusate of the carotid artery and was found to be released at a rate of 11.9±2.2 pg in 60 minutes (n=8), which was significantly decreased to 1.4±0.4 pg in 60 minutes (n=4) by cilazapril (1 μmol/L). This study provides functional evidence that tissue-generated angiotensin II and bradykinin, produced locally and in upstream arteries, control the diameter of a resistance mesenteric artery.
Endogenous Nitric Oxide Masks α
2
-Adrenergic Coronary Vasoconstriction During Exercise in the Ischemic Heart
Authors: Ishibashi Yutaka , Duncker Dirk J. , Bache Robert J.
Published: June 2012

Previously, we observed that α
1
- but not α
2
-adrenergic vasoconstriction restricted blood flow distal to a coronary artery stenosis that resulted in myocardial hypoperfusion during exercise. This study was performed to test the hypothesis that vascular smooth muscle α
2
-adrenergic vasoconstriction during exercise does exert a flow-limiting effect distal to a coronary artery stenosis but that this action is counterbalanced by simultaneous endothelial α
2
-adrenergic stimulation of NO production. Eight dogs instrumented with a Doppler velocity probe, hydraulic occluder, and indwelling microcatheter in the left anterior descending coronary artery (LAD) were studied during treadmill exercise in the presence of a coronary artery stenosis before and during infusion of the α
2
-adrenergic receptor antagonist idazoxan (1.0 μg·kg
−1
·min
−1
IC) before and after NO synthase blockade with
N
G
-monomethyl-
l
-arginine (LNNA, 1.5 mg/kg IC). Coronary pressure distal to the stenosis was maintained constant during the control period and after administration of idazoxan before and after LNNA. Neither idazoxan nor LNNA altered any of the systemic hemodynamic variables either at rest or during exercise. During exercise in the absence of a stenosis, idazoxan and LNNA had no effect on coronary blood flow. In the presence of a stenosis that decreased distal coronary pressure to 52±3 mm Hg, mean myocardial blood flow measured with microspheres was 0.87±0.17 mL·min
−1
·g
−1
in the LAD-dependent region and 2.52±0.30 mL·min
−1
·g
−1
in the posterior control region, respectively. With no change in distal coronary pressure, idazoxan had no effect on mean myocardial blood flow in the LAD region (0.86±0.17 mL·min
−1
·g
−1
), but LNNA decreased mean myocardial blood flow to 0.49±0.09 (
P
<.01). However, when idazoxan was infused during exercise in the presence of a coronary artery stenosis after LNNA administration, idazoxan increased mean myocardial blood flow to 0.62±0.13 mL·min
−1
·g
−1
(
P
<.01). These data demonstrate that α
2
-adrenergic stimulation of endothelial NO production, which occurs during exercise in the presence of a flow-limiting coronary artery stenosis, acts to counterbalance vascular smooth muscle α
2
-adrenergic vasoconstriction.