bluuebunny/crossref_metadata_2025 huggingface dataset:
Expression of heteromeric amino acid transporters along the murine intestine
Authors: Dave Mital H. , Schulz Nicole , Zecevic Marija , Wagner Carsten A. , Verrey Francois
Published: May 2004

Members of the new heterodimeric amino acid transporter family are composed of two subunits, a catalytic multitransmembrane spanning protein (light chain) and a type II glycoprotein (heavy chain). These transporters function as exchangers and thereby extend the transmembrane amino acid transport selectivity to specific amino acids. The heavy chain rBAT associates with the light chain b°,+AT to form a cystine and cationic amino acid transporter. The other heavy chain, 4F2hc, can interact with seven different light chains to form various transporters corresponding to systems L, y+L, asc or x−c. The importance of some of these transporters in intestinal and renal (re)absorption of amino acids is highlighted by the fact that mutations in either the rBAT or b°,+AT subunit result in cystinuria whereas a defect in the y+‐LAT1 light chain causes lysinuric protein intolerance. Here we investigated the localization of these transporters in intestine since both diseases are also characterized by altered intestinal amino acid absorption. Real time PCR showed organ‐specific expression patterns for all transporter subunit mRNAs along the intestine and Western blotting confirmed these findings on the protein level. Immunohistochemistry demonstrated basolateral coexpression of 4F2hc, LAT2 and y+‐LAT1 in stomach and small intestine, whereas rBAT and b°,+AT were found colocalizing on the apical side of small intestine epithelium. In stomach, 4F2hc and LAT2 were localized in H+/K+‐ATPase‐expressing parietal cells. The abundant expression of several members of the heterodimeric transporter family along the murine small intestine suggests their involvement in amino acids absorption. Furthermore, strong expression of rBAT, b°,+AT and y+‐LAT1 in the small intestine explains the reduced intestinal absorption of some amino acid in patients with cystinuria or lysinuric protein intolerance.
Sequential activation of RhoA and FAK/paxillin leads to ATP release and actin reorganization in human endothelium
Authors: Hirakawa Masakazu , Oike Masahiro , Karashima Yuji , Ito Yushi
Published: May 2004

We have investigated the cellular mechanisms of mechanical stress‐induced immediate responses in human umbilical vein endothelial cells (HUVECs). Hypotonic stress (HTS) induced ATP release, which evoked a Ca2+ transient, followed by actin reorganization within a few minutes, in HUVECs. Disruption of the actin cytoskeleton did not suppress HTS‐induced ATP release, and inhibition of the ATP‐mediated Ca2+ response did not affect actin reorganization, thereby indicating that these two responses are not interrelated. ATP release and actin reorganization were also induced by lysophosphatidic acid (LPA). HTS and LPA induced membrane translocation of RhoA, which occurs when RhoA is activated, and tyrosine phosphorylation of focal adhesion kinase (FAK) and paxillin. Tyrosine kinase inhibitors (herbimycin A or tyrphostin 46) inhibited both HTS‐ and LPA‐induced ATP release and actin reorganization, but did not affect RhoA activation. In contrast, Rho‐kinase inhibitor (Y27632) inhibited all of the HTS‐ and LPA‐induced responses. These results indicate that the activation of the RhoA/Rho‐kinase pathway followed by tyrosine phosphorylation of FAK and paxillin leads to ATP release and actin reorganization in HUVECs. Furthermore, the fact that HTS and LPA evoke exactly the same intracellular signals and responses suggests that even these immediate mechanosensitive responses are in fact not mechanical stress‐specific.
Abrupt Tropical Vegetation Response to Rapid Climate Changes
Authors: Hughen Konrad A. , Eglinton Timothy I. , Xu Li , Makou Matthew
Published: May 2004

Identifying leads and lags between high- and low-latitude abrupt climate shifts is needed to understand where and how such events were triggered. Vascular plant biomarkers preserved in Cariaco basin sediments reveal rapid vegetation changes in northern South America during the last deglaciation, 15,000 to 10,000 years ago. Comparing the biomarker records to climate proxies from the same sediment core provides a precise measure of the relative timing of changes in different regions. Abrupt deglacial climate shifts in tropical and high-latitude North Atlantic regions were synchronous, whereas changes in tropical vegetation consistently lagged climate shifts by several decades.
DEALING WITH SKIN MOTION AND WOBBLING MASSES IN INVERSE DYNAMICS
Authors: GÜNTHER MICHAEL , SHOLUKHA VIKTOR A. , KESSLER DANNY , WANK VEIT , BLICKHAN REINHARD
Published: May 2004

Inverse dynamics is a standard analysis in biomechanics to reconstruct time histories of internal driving forces and torques from measured external forces and segmental kinematics. The main sources of inconsistency leading to analytical artefacts in this process are skin marker and soft tissue motion. These potentially artificial high frequency fluctuations in the joint torques may serve as an erroneous basis of (misleading) assumptions with respect to muscular activity. Here we suggest techniques to reduce these errors. In both parts of this study, high-speed video and force platform data were acquired. In one part, 69 sequences of human barefoot running were sampled followed by an inverse dynamic analysis of the stance leg. The time history of the hip joint torque in the sagittal plane served as a sensitive "detector" of dynamic analysis artefacts. We show that the most important error — the relative skin to bone motion especially of the knee marker — can be reduced significantly by processing kinematic data using bone rigidity (constant segment lengths) and bony contour (frontal knee edge) information. Further on, neglecting significantly initiated soft tissue dynamics in the inverse dynamic model introduces another inconsistency in the analytical process. Therefore, in a second part of this study, soft tissue kinematics from 14 jumping sequences were identified. These data provided a set of coupling parameters of wobbling masses to the bone that were ready to be implemented in the inverse dynamic model. Using realistic bone kinematics mainly avoids phase shifts in the acceleration scenario within the leg, and thus artifical hip torque fluctuations within the whole contact period. In human running, accounting for soft tissue dynamics mainly affects the calculated timing of the hip joint torque during the impact phase.
STATES AS LABORATORIES: A Reprise
Authors: Morehouse Sarah M. , Jewell Malcolm E.
Published: May 2004

▪ Abstract  As laboratories, states are faced with a new agenda of social experimentation. This article first considers state elections and parties, including state realignment, party endorsements and primary elections, uncontested seats, and campaign finance. A second topic is the governorship, including governors' careers, changes in power, party leadership, and legislative programs and tactics used in negotiating with legislators. A third section considers the state legislatures, including term limits, professionalism, leadership, committees, roll-call voting, and representation. Another subject closely related to all aspects is the variety and organization of interest groups, their power, and whom they represent. The conclusion is that the states as laboratories are now equipped to handle the social experimentation that devolution has handed down to them.
OAKESHOTT AND POLITICAL SCIENCE
Authors: Minogue Kenneth
Published: May 2004

▪ Abstract  Michael Oakeshott (1901–1990) achieved arguably the most sophisticated philosophical understanding of politics in recent times. His characteristic skepticism extended to the possibility of creating a genuine science of politics. This chapter sketches the development of his conception of political understanding. It begins with his early elaboration of the modal character of all knowledge, discusses his criticism of rationalism and reflections on the appropriate curriculum for studying politics in a university. It concludes by examining the theoretical basis of his rejection of the idea that politics could be analyzed as a field governed by natural laws.
Expression and localization of rat NBC4c in liver and renal uroepithelium
Authors: Abuladze Natalia , Pushkin Alexander , Tatishchev Sergei , Newman Debra , Sassani Pakan , Kurtz Ira
Published: May 2004

Previous studies provided functional evidence for electrogenic Na+-HCO3− cotransport in hepatocytes and in intrahepatic bile duct cholangiocytes. The molecular identity of the transporters mediating electrogenic sodium-bicarbonate cotransport in the liver is currently unknown. Of the known electrogenic Na+-HCO3− cotransporters (NBC1 and NBC4), we previously showed that NBC4 mRNA is highly expressed in the liver. In the present study, we performed RT-PCR, immunoblotting, and immunohistochemistry to characterize the expression pattern of NBC4 in rat liver and kidney. For immunodetection, a polyclonal antibody against rat NBC4 was generated and affinity purified. Of the known human NBC4 variants, only the rat NBC4c ortholog was detected by RT-PCR in rat liver, and the molecular mass of the NBC4c protein was ∼145 kDa. NBC4c protein was expressed in hepatocytes and in the cholangiocytes lining the intrahepatic bile ducts. In hepatocytes, NBC4c was localized to the basolateral plasma membrane, whereas intrahepatic cholangiocytes stained apically. The NBC1 electrogenic sodium cotransporter variants kNBC1 and pNBC1 were not detected by immunoblotting and immunohistochemistry in rat liver. The pattern of localization of NBC4c in the liver suggests that the cotransporter plays a role in mediating Na+-HCO3− cotransport in hepatocytes and intrahepatic cholangiocytes. Unlike the liver, the rat kidney expressed electrogenic sodium-bicarbonate cotransporter proteins kNBC1 and NBC4c. In kidney, NBC4c also had a molecular mass of ∼145 kDa and was immunolocalized to uroepithelial cells lining the renal pelvis, where the cotransporter may play an important role in protecting the renal parenchyma from alterations in urine pH.
Cytokine regulation of skeletal muscle fatty acid metabolism: effect of interleukin-6 and tumor necrosis factor-α
Authors: Bruce Clinton R. , Dyck David J.
Published: May 2004

IL-6 and TNF-α have been associated with insulin resistance and type 2 diabetes. Furthermore, abnormalities in muscle fatty acid (FA) metabolism are strongly associated with the development of insulin resistance. However, few studies have directly examined the effects of either IL-6 or TNF-α on skeletal muscle FA metabolism. Here, we used a pulse-chase technique to determine the effect of IL-6 (50–5,000 pg/ml) and TNF-α (50–5,000 pg/ml) on FA metabolism in isolated rat soleus muscle. IL-6 (5,000 pg/ml) increased exogenous and endogenous FA oxidation by ∼50% ( P < 0.05) but had no effect on FA uptake or incorporation of FA into endogenous lipid pools. In contrast, TNF-α had no effect on FA oxidation but increased FA incorporation into diacylglycerol (DAG) by 45% ( P < 0.05). When both IL-6 (5,000 pg/ml) and insulin (10 mU/ml) were present, IL-6 attenuated insulin's suppressive effect on FA oxidation, increasing exogenous FA oxidation (+37%, P < 0.05). Furthermore, in the presence of insulin, IL-6 reduced the esterification of FA to triacylglycerol by 22% ( P < 0.05). When added in combination with IL-6 or leptin (10 μg/ml), the TNF-α-induced increase in DAG synthesis was inhibited. In conclusion, the results demonstrate that IL-6 plays an important role in regulating fat metabolism in muscle, increasing rates of FA oxidation, and attenuating insulin's lipogenic effects. In contrast, TNF-α had no effect on FA oxidation but increased FA incorporation into DAG, which may be involved in the development of TNF-α-induced insulin resistance in skeletal muscle.
Smooth muscle overexpression of IGF-I induces a novel adaptive response to small bowel resection
Authors: Knott Andrew W. , Juno Russell J. , Jarboe Marcus D. , Profitt Sherri A. , Erwin Christopher R. , Smith Eric P. , Fagin James A. , Warner Brad W.
Published: May 2004

Prior studies of intestinal adaptation after massive small bowel resection (SBR) have focused on growth factors and their effects on amplification of the gut mucosa. Because adaptive changes have also been described in intestinal smooth muscle, we sought to determine the effect of targeted smooth muscle growth factor overexpression on resection-induced intestinal adaptation. Male transgenic mice with smooth muscle cell overexpression of insulin-like growth factor I (IGF-I) by virtue of an α-smooth muscle actin promoter were obtained. SMP8 IGF-I transgenic (IGF-I TG) and nontransgenic (NT) littermates underwent 50% proximal SBR or sham operation and were then killed after 3 or 28 days. NT mice showed the expected alterations in mucosal adaptive parameters after SBR, such as increased wet weight and villus height. The IGF-I TG mice had inherently taller villi, which did not increase significantly after SBR. In addition, IGF-I TG mice had a 50% postresection persistent increase in remnant intestinal length, which was associated with an early decline and later increase in relative mucosal surface area. These results indicate that growth factor overexpression within the muscularis layer of the bowel wall induces significant postresection adaptive intestinal lengthening and a unique mucosal response. IGF-I signaling within the muscle wall may play an important role in the pathogenesis of resection-induced adaptation.
Virtual electrode theory explains pacing threshold increase caused by cardiac tissue damage
Authors: Sambelashvili Aleksandre T. , Nikolski Vladimir P. , Efimov Igor R.
Published: May 2004

The virtual electrode polarization (VEP) effect is believed to play a key role in electrical stimulation of heart muscle. However, under certain conditions, including clinically, its existence and importance remain unknown. We investigated the influence of acute tissue damage produced by continuous pacing with strong current (40-mA, 4-ms biphasic pulses with 4-Hz frequency for 5 min) on stimulus-generated VEPs and pacing thresholds. A fluorescent optical mapping technique was used to obtain stimulus-induced transmembrane potential distribution around a pacing electrode applied to the ventricular surface of a Langendorff-perfused rabbit heart ( n = 5). Maps and pacing thresholds were recorded before and after tissue damage. Spatial extents of electroporation and cell uncoupling were assessed by propidium iodide ( n = 2) and connexin43 ( n = 3) antibody staining, respectively. On the basis of these data, passive and active three-dimensional bidomain models were built to determine VEP patterns and thresholds for different-sized areas of the damaged region. Electrophysiological results showed that acute tissue damage led to disappearance of the VEP with an associated significant increase in pacing thresholds. Damage was expressed in electroporation and cell uncoupling within a ∼1.0-mm-diameter area around the tip of the electrode. According to computer simulations, cell uncoupling, rather than electroporation, might be the direct cause of VEP elimination and threshold increase, which was nonlinearly dependent on the size of the damaged region. Fiber rotation with depth did not substantially affect the numerical results. The study explains failure to stimulate damaged tissue within the concepts of the VEP theory.
In vivo role of heme oxygenase in ischemic coronary vasodilation
Authors: Nishikawa Yasuhiro , Stepp David W. , Merkus Daphne , Jones Deron , Chilian William M.
Published: May 2004

The heart constitutively expresses heme oxygenase (HO)-2, which catabolizes heme-containing proteins to produce biliverdin and carbon monoxide (CO). The heart also contains many possible substrates for HO-2 such as heme groups of myoglobin and cytochrome P-450s, which potentially could be metabolized into CO. As a result of observations that CO activates guanylyl cyclase and induces vascular relaxation and that HO appears to confer protection from ischemic injury, we hypothesized that the HO-CO pathway is involved in ischemic vasodilation in the coronary microcirculation. Responses of epicardial coronary arterioles to ischemia (perfusion pressure ∼40 mmHg; flow velocity decreased by ∼50%; d L/d t reduced by ∼60%) were measured using stroboscopic fluorescence microangiography in 34 open-chest anesthetized dogs. Ischemia caused vasodilation of coronary arterioles by 36 ± 6%. Administration of NG-monomethyl-l-arginine (l-NMMA, 3 μmol·kg−1·min−1 intracoronary), indomethacin (10 mg/kg iv), and K+ (60 mM, epicardial suffusion) to prevent the actions of nitric oxide, prostaglandins, and hyperpolarizing factors, respectively, partially inhibited dilation during ischemia (36 ± 6 vs. 15 ± 4%; P < 0.05). The residual vasodilation during ischemia after antagonist administration was inhibited by tin mesoporphyrin IX (SnMP, 10 mg/kg iv), which is an inhibitor of HO (15 ± 4 vs. 7 ± 2%; P < 0.05 vs. before SnMP). The guanylyl cyclase inhibitor 1 H-[1,2,4]oxadiazole[4,3- a]quinoxalin-1-one (10−5 M, epicardial suffusion) also inhibited vasodilation during ischemia in the presence of l-NMMA with indomethacin and KCl. Moreover, administration of heme-l-arginate, which is a substrate for HO, produced dilation after ischemia but not after control conditions. We conclude that during myocardial ischemia, HO-2 activation can produce cGMP-mediated vasodilation presumably via the production of CO. This vasodilatory pathway appears to play a backup role and is activated only when other mechanisms of vasodilation during ischemia are exhausted.
Vascular endothelial growth factor stimulates differential signaling pathways in in vivo microcirculation
Authors: Aramoto Haruo , Breslin Jerome W. , Pappas Peter J. , Hobson Robert W. , Durán Walter N.
Published: May 2004

Vascular endothelial growth factor (VEGF) induces mild vasodilation and strong increases in microvascular permeability. Using intravital microscopy and digital integrated optical intensity image analysis, we tested, in the hamster cheek pouch microcirculation, the hypothesis that differential signaling pathways in arterioles and venules represent an in vivo regulatory mechanism in the control of vascular diameter and permeability. The experimental design involved blocking specific signaling molecules and simultaneously assessing VEGF-induced changes in arteriolar diameter and microvascular transport of FITC-Dextran 150. Inhibition of Akt [indirectly via phosphatidylinositol 3-kinase with LY-294002 or wortmannin] or PKC (with bisindolylmaleimide) reduced VEGF-induced hyperpermeability. However, phosphatidylinositol 3-kinase/Akt inhibition enhanced the early phase and attenuated the late phase of VEGF-induced vasodilation, whereas blocking PKC had no effect. Inhibition of extracellular signal-regulated kinase (ERK)-1/2 (with PD-98059 or AG-126) also reduced VEGF-induced hyperpermeability but did not block VEGF-induced vasodilation. Blockade of endothelial nitric oxide synthase (with Nω-monomethyl-l-arginine) inhibited VEGF-induced changes in both permeability and diameter. Furthermore, immunofluorescence studies with human umbilical vein endothelial cells revealed that bisindolylmaleimide, PD-98059, and l-NMMA attenuate VEGF-induced reorganization of vascular endothelial cadherin. Our data demonstrate that 1) endothelial nitric oxide synthase is a common convergence pathway for VEGF-induced changes in arteriolar diameter and microvascular permeability; 2) PKC and ERK-1/2 do not play a major role in VEGF-induced vasodilation in the hamster cheek pouch microcirculation; and 3) Akt, PKC, and ERK-1/2 are elements of the signaling cascade that regulates VEGF-stimulated microvascular hyperpermeability. Our data provide evidence for differential signaling as a regulatory step in VEGF-stimulated microvascular dynamics.
Autonomic regulation of calcium and potassium channels is oppositely modulated by microtubules in cardiac myocytes
Authors: Gómez Ana M. , Kerfant Benoît-Gilles , Vassort Guy , Pappano Achilles J.
Published: May 2004

We recently showed that colchicine treatment of rat ventricular myocytes increases the L-type Ca2+current ( ICa) and intracellular Ca2+concentration ([Ca2+]i) transients and interferes with adrenergic signaling. These actions were ascribed to adenylyl cyclase (AC) stimulation after Gsactivation by α,β-tubulin. Colchicine depolymerizes microtubules into α,β-tubulin dimers. This study analyzed muscarinic signals in myocytes with intact or depolymerized microtubules. Myocytes were loaded with the Ca2+indicator fluo 3 and were field stimulated at 1 Hz or voltage clamped. In untreated cells, carbachol (CCh; 1 μM) induced ACh-activated K+current [ IK(ACh)], which happens via βγ-subunits from the activation of Gi. Carbachol also reduced [Ca2+]itransients and contractions. Once Giis activated by muscarinic agonist, the αi-subunit is released from the βγ-subunits, but it is silent, and its inhibition of the AC/cAMP cascade, manifested by ICareduction, is not seen unless AC has been previously activated. In colchicine-treated cells, CCh caused greater reductions of [Ca2+]itransients and contractions than in untreated cells. The αi-subunit became effective in signaling through the AC/cAMP cascade and reduced ICawithout changing its voltage-dependence. Isoproterenol (Iso) regained its efficacy and reversed ICainhibition by CCh. Stimulation of ICaby forskolin persisted in colchicine-treated cells when Iso was ineffective. The effect of CCh on IK(ACh)was occluded in colchicine-treated cells. Colchicine treatment, per se, may increase IK(ACh)by βγ-subunits released from Gsto mask this effect of CCh. Microtubules suppress ICaregulation by αi; their disruption releases restraints that unmask muscarinic inhibition of ICa. Summarily, colchicine treatment reverses regulation of ventricular excitation-contraction coupling by autonomic agents.
Comparative analysis of parvalbumin and SERCA2a cardiac myocyte gene transfer in a large animal model of diastolic dysfunction
Authors: Hirsch Jennifer C. , Borton Andrea R. , Albayya Faris P. , Russell Mark W. , Ohye Richard G. , Metzger Joseph M.
Published: May 2004

Diastolic dysfunction results from impaired ventricular relaxation and is an important component of human heart failure. Genetic modification of intracellular calcium-handling proteins may hold promise to redress diastolic dysfunction; however, it is unclear whether other important aspects of myocyte function would be compromised by this approach. Accordingly, a large animal model of humanlike diastolic dysfunction was established through 1 yr of left ventricular (LV) pressure overload by descending thoracic aortic coarctation in canines. Serial echocardiography documented a progressive increase in LV mass. Diastolic dysfunction with preserved systolic function was evident at the whole organ and myocyte levels in this model, as determined by hemispheric sonomicrometric piezoelectric crystals, pressure transducer catheterization, and isolated myocyte studies. Gene transfer of the sarco(endo)plasmic reticulum calcium-ATPase (SERCA2a) and parvalbumin (Parv), a fast-twitch skeletal muscle Ca2+ buffer, restored cardiac myocyte relaxation in a dose-dependent manner under baseline conditions. At high Parv concentrations, sarcomere shortening was depressed. In contrast, during β-adrenergic stimulation, the expected enhancement of myocyte contraction (inotropy) was abrogated by SERCA2a but not by Parv. The mechanism of this effect is unknown, but it could relate to the uncoupling of SERCA2a/phospholamban in SERCA2a myocytes. Considering that inotropy is vital to overall cardiac performance, the divergent effects of SERCA2a and Parv reported here could impact potential therapeutic strategies for human heart failure.
Effect of acute global ischemia on the upper limit of vulnerability: a simulation study
Authors: Rodríguez Blanca , Tice Brock M. , Eason James C. , Aguel Felipe , Ferrero José M. , Trayanova Natalia
Published: May 2004

The goal of this modeling research is to provide mechanistic insight into the effect of altered membrane kinetics associated with 5–12 min of acute global ischemia on the upper limit of cardiac vulnerability (ULV) to electric shocks. We simulate electrical activity in a finite-element bidomain model of a 4-mm-thick slice through the canine ventricles that incorporates realistic geometry and fiber architecture. Global acute ischemia is represented by changes in membrane dynamics due to hyperkalemia, acidosis, and hypoxia. Two stages of acute ischemia are simulated corresponding to 5–7 min ( stage 1) and 10–12 min ( stage 2) after the onset of ischemia. Monophasic shocks are delivered in normoxia and ischemia over a range of coupling intervals, and their outcomes are examined to determine the highest shock strength that resulted in induction of reentrant arrhythmia. Our results demonstrate that acute ischemia stage 1 results in ULV reduction to 0.8A from its normoxic value of 1.4A. In contrast, no arrhythmia is induced regardless of shock strength in acute ischemia stage 2. An investigation of mechanisms underlying this behavior revealed that decreased postshock refractoriness resulting mainly from 1) ischemic electrophysiological substrate and 2) decrease in the extent of areas positively-polarized by the shock is responsible for the change in ULV during stage 1. In contrast, conduction failure is the main cause for the lack of vulnerability in acute ischemia stage 2. The insight provided by this study furthers our understanding of mechanisms by which acute ischemia-induced changes at the ionic level modulate cardiac vulnerability to electric shocks.
Endothelial monocyte-activating polypeptide II causes NOS-dependent pulmonary artery vasodilation: a novel effect for a proinflammatory cytokine
Authors: Tsai Ben M. , Wang Meijing , Clauss Matthias , Sun Peichuan , Meldrum Daniel R.
Published: May 2004

Endothelial monocyte-activating polypeptide (EMAP) II is a novel proinflammatory cytokine that is released from apoptotic and hypoxic cells. The purpose of this study was to determine the effect of EMAP II on the pulmonary artery (PA) and to characterize its mechanism of action. To study this, isolated PA rings from adult male Sprague-Dawley rats were suspended on steel hooks connected to force transducers and immersed in 37°C organ baths containing modified Krebs-Henseleit solution. After equilibration, force displacement of phenylephrine-preconstricted PA was measured in response to EMAP II. Experiments were performed in endothelium-intact rings, endothelium-denuded rings, and in the presence of the NOS inhibitor Nω-nitro-l-arginine methyl ester (l-NAME). Pulmonary artery rings were then subjected to quantitative PCR analysis for inducible NOS (iNOS) mRNA. EMAP II caused a maximal vasodilation of 251 ± 30.7 mg in endothelium-intact PA. EMAP II caused no vasodilation in endothelium-denuded and l-NAME-treated PA (20 ± 14.0 mg and 17.5 ± 7.5 mg, respectively, P < 0.001 vs. endothelium intact). In addition to its vasoactive properties, EMAP II increased PA iNOS mRNA twofold compared with controls. These results demonstrate that 1) EMAP II causes PA vasodilation; 2) EMAP II-mediated PA vasodilation is endothelium dependent and NOS dependent; and 3) EMAP II upregulates iNOS mRNA expression in PA. This report constitutes the first demonstration of EMAP II's effects on the pulmonary artery, its mechanism of action, and represents the identification of the first proinflammatory cytokine to cause PA vasodilation.
Prolonged exercise to fatigue in humans impairs skeletal muscle Na+-K+-ATPase activity, sarcoplasmic reticulum Ca2+release, and Ca2+uptake
Authors: Leppik James A. , Aughey Robert J. , Medved Ivan , Fairweather Ian , Carey Michael F. , McKenna Michael J.
Published: May 2004

Prolonged exhaustive submaximal exercise in humans induces marked metabolic changes, but little is known about effects on muscle Na+-K+-ATPase activity and sarcoplasmic reticulum Ca2+regulation. We therefore investigated whether these processes were impaired during cycling exercise at 74.3 ± 1.2% maximal O2uptake (mean ± SE) continued until fatigue in eight healthy subjects (maximal O2uptake of 3.93 ± 0.69 l/min). A vastus lateralis muscle biopsy was taken at rest, at 10 and 45 min of exercise, and at fatigue. Muscle was analyzed for in vitro Na+-K+-ATPase activity [maximal K+-stimulated 3- O-methylfluorescein phosphatase (3- O-MFPase) activity], Na+-K+-ATPase content ([3H]ouabain binding sites), sarcoplasmic reticulum Ca2+release rate induced by 4 chloro- m-cresol, and Ca2+uptake rate. Cycling time to fatigue was 72.18 ± 6.46 min. Muscle 3- O-MFPase activity (nmol·min−1·g protein−1) fell from rest by 6.6 ± 2.1% at 10 min ( P < 0.05), by 10.7 ± 2.3% at 45 min ( P < 0.01), and by 12.6 ± 1.6% at fatigue ( P < 0.01), whereas3[H]ouabain binding site content was unchanged. Ca2+release (mmol·min−1·g protein−1) declined from rest by 10.0 ± 3.8% at 45 min ( P < 0.05) and by 17.9 ± 4.1% at fatigue ( P < 0.01), whereas Ca2+uptake rate fell from rest by 23.8 ± 12.2% at fatigue ( P = 0.05). However, the decline in muscle 3- O-MFPase activity, Ca2+uptake, and Ca2+release were variable and not significantly correlated with time to fatigue. Thus prolonged exhaustive exercise impaired each of the maximal in vitro Na+-K+-ATPase activity, Ca2+release, and Ca2+uptake rates. This suggests that acutely downregulated muscle Na+, K+, and Ca2+transport processes may be important factors in fatigue during prolonged exercise in humans.
Viral Delivery of NR2D Subunits Reduces Mg2+Block of NMDA Receptor and Restores NT-3-Induced Potentiation of AMPA-Kainate Responses in Maturing Rat Motoneurons
Authors: Arvanian Victor L. , Bowers William J. , Petruska Jeffrey C. , Motin Vladimir , Manuzon Honeyleen , Narrow Wade C. , Federoff Howard J. , Mendell Lorne M.
Published: May 2004

N-methyl-d-aspartate (NMDA) responsiveness of motoneurons declines during the initial 2 postnatal weeks due to increasing Mg2+block of NMDA receptors. Using gene chip analyses, RT-PCR, and immunochemistry, we have shown that the NR2D subunit of the NMDA receptor (NMDAR), known to confer resistance to Mg2+block, also declines in motoneurons during this period. We injected a viral construct (HSVnr2d) into the lumbar spinal cord on postnatal day 2 in an attempt to restore NMDAR function in motoneurons during the second postnatal week. Following HSVnr2d injection, we detected elevated levels of NR2D mRNA in spinal cord samples and NR2D protein specifically in motoneurons. These molecular changes were associated with marked functional alterations whereby NMDAR-mediated responses in motoneurons associated with both dorsal root (DR) and ventrolateral funiculus (VLF) inputs returned to values observed at E18 due to decreased Mg2+blockade. Viruses carrying the β-galactosidase gene did not induce these effects. NT-3 is known to potentiate AMPA-kainate responses in motoneurons if the response has an NMDAR-mediated component and thus is normally ineffective during the second postnatal week. Restoration of NMDAR-mediated responsiveness in the second postnatal week was accompanied by a return of the ability of neurotrophin-3 (NT-3) to potentiate the AMPA-kainate responses produced by both DR and VLF synaptic inputs. We conclude that delivery of the gene for a specific NMDA subunit can restore properties characteristic of younger animals to spinal cord motoneurons. This approach might be useful for enhancing the function of fibers surviving in the damaged spinal cord.
Proton Modulation of α1β3δ GABAA Receptor Channel Gating and Desensitization
Authors: Feng Hua-Jun , Macdonald Robert L.
Published: May 2004

αβγ GABAA receptor currents are phasic and desensitizing, whereas αβδ GABAA receptor currents are tonic and have no fast desensitization. αβγ receptors are subsynaptic and mediate phasic inhibition, whereas αβδ receptors are extra- or perisynaptic and mediate tonic inhibition. Given the different roles of these GABAA receptor isoforms and the fact that GABAA receptors are allosterically regulated by extracellular pH in a subunit-dependent manner, we compared the effects of changing pH on rat δ or γ2L subunit–containing GABAA receptor currents. Human embryonic kidney cells (HEK293T) were transfected with cDNAs encoding rat α1, β3, γ2L, or δ GABAA receptor subunits in several binary and ternary combinations, and whole cell and single channel patch-clamp recordings were obtained. Lowering pH substantially enhanced α1β3 receptor currents. This effect was significantly more pronounced for ternary α1β3δ receptors, whereas ternary α1β3γ2L receptors were relatively insensitive to lowered pH. Lowering pH did not affect the extent of desensitization of α1β3 and α1β3γ2L receptor currents, but significantly increased the extent of desensitization of α1β3δ receptor currents. Lowering pH prolonged deactivation of α1β3 and α1β3δ receptor currents and enhanced the “steady-state” currents of α1β3δ receptors evoked by long-duration (28 s) GABA applications. Lowering pH significantly increased mean open duration of α1β3δ steady-state single channel currents due to introduction of a longer-duration open state, suggesting that low pH enhances α1β3δ receptor steady-state currents by modifying GABAA receptor gating properties.
Darboux‐Lamé equation and isomonodromic deformation
Authors: Ohmiya Mayumi
Published: May 2004

The Darboux‐Lamé equation is defined as the double Darboux
transformation of the Lamé equation, and is studied from the
viewpoint of the isomonodromic deformation theory. It is shown
that the second‐order ordinary differential equation of Fuchsian
type on P1 correspondingto the second
Darboux‐Lamé equation is obtained as isomonodromic
deformation of some specific Gauss′ hypergeometric differential
equation.
Efficient criteria for the stabilization of planar linear systems by hybrid feedback controls
Authors: Litsyn Elena , Myasnikova Marina , Nepomnyashchikh Yurii , Ponosov Arcady
Published: May 2004

We suggest some criteria for the stabilization of planar linear systems via linear hybrid feedback controls. The results are formulated in terms of the input matrices. For instance, this enables us to work out an algorithm which is directly suitable for a computer realization. At the same time, this algorithm helps to check easily if a given linear 2 × 2 system can be stabilized (a) by a linear ordinary feedback control or (b) by a linear hybrid feedback control.
Balance Between PGD Synthase and PGE Synthase Is a Major Determinant of Atherosclerotic Plaque Instability in Humans
Authors: Cipollone Francesco , Fazia Maria , Iezzi Annalisa , Ciabattoni Giovanni , Pini Barbara , Cuccurullo Chiara , Ucchino Sante , Spigonardo Francesco , De Luca Mariella , Prontera Cesaria , Chiarelli Francesco , Cuccurullo Franco , Mezzetti Andrea
Published: May 2004

Objective—Inducible cyclooxygenase (COX-2) catalyzes the first step in prostanoid biosynthesis and is considered a proinflammatory enzyme. COX-2 and type 1 inducible PGE synthase (mPGES-1) have a role in metalloproteinase (MMP) release leading to plaque rupture. In contrast, lipocalin-type PGD synthase (L-PGDS) has been shown to exert antiinflammatory actions. Thus, in this study we investigated whether a shift from a PGDS-oriented to a PGES-oriented profile in arachidonate metabolism leads to inflammatory activation in rupture-prone plaque macrophages.

Methods and Results—Atherosclerotic plaques were obtained from 60 patients who underwent carotid endarterectomy, symptomatic (n=30) and asymptomatic (n=30) according to evidence of recent transient ischemic attack or stroke. Plaques were analyzed for COX-2, mPGES-1, L-PGDS, PPARγ, IκBα, NF-κB, and MMP-9 by immunocytochemistry, Western blot, reverse-transcriptase polymerase chain reaction, enzyme immunoassay, and zymography. Prostaglandin E2(PGE2) pathway was significantly prevalent in symptomatic plaques, whereas PGD2pathway was overexpressed in asymptomatic ones, associated with NF-κB inactivation and MMP-9 suppression. In vitro COX-2 inhibition in monocytes was associated with reduced MMP-9 release only when PGD2pathway overcame PGE2pathway.

Conclusions—These results suggest that COX-2 may have proinflammatory and antiinflammatory properties as a function of expression of downstream PGH2isomerases, and that the switch from L-PGDS to mPGES-1 in plaque macrophages is associated with cerebral ischemic syndromes, possibly through MMP-induced plaque rupture.
Determinants of Arterial Nitrate-Mediated Dilatation in Children
Authors: Järvisalo Mikko J. , Lehtimäki Terho , Raitakari Olli T.
Published: May 2004

Background—

Impaired arterial dilatation response to nitroglycerin has been observed in adults with risk factors for atherosclerosis and in patients with established atherosclerotic disease. This defect parallels changes in vascular endothelial function and may be attributed to increased oxidative stress. Because atherosclerosis begins in childhood, we examined the correlates of nitrate-mediated dilatation (NMD) in children, including brachial artery endothelial function, oxidized LDL, and carotid artery intima-media thickness (IMT).

Methods and Results—

Brachial artery flow-mediated endothelium-dependent dilatation (FMD) and nitrate-mediated smooth muscle function, IMT of the carotid bulb, and brachial artery and oxidized LDL were measured in 142 children (mean age, 11 years; range, 8 to 17 years), including 87 healthy children, 41 diabetic children, and 14 children with familial hypercholesterolemia. NMD correlated directly with FMD (
r
=0.46,
P
<0.001) and inversely with brachial artery baseline diameter (
r
=−0.36,
P
<0.001), age (
r
=−0.25,
P
=0.003), body mass index (
r
=−0.31,
P
<0.001), diabetes (
r
=−0.22,
P
=0.008), oxidized LDL (
r
=−0.18,
P
=0.045), and IMT (
r
=−0.33,
P
<0.001). In a multivariate regression model, the significant correlates for NMD were FMD response (β=0.003,
P
<0.001), brachial artery diameter (β=−0.03,
P
=0.01), oxidized LDL (β=−0.07,
P
=0.02), and IMT (β=−0.15,
P
=0.03).

Conclusions—

Reduced endothelial function, increased oxidative stress, and preclinical carotid atherosclerosis are independent determinants of impaired NMD in children. These data thus suggest that primary nitrate tolerance occurs in children at risk for atherosclerosis.
Serum Total Homocysteine Concentrations and Risk of Stroke and Its Subtypes in Japanese
Authors: Iso Hiroyasu , Moriyama Yuri , Sato Shinichi , Kitamura Akihiko , Tanigawa Takeshi , Yamagishi Kazumasa , Imano Hironori , Ohira Tetsuya , Okamura Tomonori , Naito Yoshihiko , Shimamoto Takashi
Published: May 2004

Background—

To date, no prospective studies have examined the association between serum homocysteine levels and the risk of stroke and stroke subtypes in Asian populations.

Methods and Results—

A prospective, nested, case-control study of Japanese subjects 40 to 85 years of age was conducted by using frozen serum samples from 11 846 participants in cardiovascular risk surveys collected from 1984 to 1995 for one community and 1989 to 1995 for the other two communities. By the end of 2000, we identified 150 incident strokes, the subtypes of which were confirmed by imaging studies. Three control subjects per case were selected by matching for sex, age, community, year of serum storage, and fasting status. Serum total homocysteine levels were measured by high-performance liquid chromatography. Compared with control subjects, total (n=150), hemorrhagic (n=52), and ischemic (n=98) strokes had higher geometric mean values of total homocysteine and higher proportions of homocysteine ≥11.0 μmol/L. The multivariate odds ratios (95% CI) for highest (≥11.0 μmol/L) versus lowest quartiles (<7.0 μmol/L) of homocysteine after adjustment for body mass index, smoking, alcohol intake, hypertension, serum total cholesterol, and other cardiovascular risk factors were 2.99 (1.51 to 5.93) for total stroke, 3.89 (1.60 to 9.46) for ischemic stroke, 3.36 (1.27 to 8.90) for lacunar infarction, and 1.63 (0.44 to 6.00) for hemorrhagic stroke. The respective multivariate odds ratios associated with a 5-μmol/L increase in homocysteine were 1.40 (1.09 to 1.80), 1.52 (1.07 to 2.14), 1.48 (1.01 to 2.18), and 1.10 (0.76 to 1.59). The excess risk of total and ischemic strokes did not vary significantly according to sex, age, smoking status, or hypertensive status.

Conclusions—

High total homocysteine concentrations were associated with the increased risk of total stroke, more specifically ischemic stroke and lacunar infarction, among Japanese men and women.
Effect of Cardiac Myosin Binding Protein-C on Mechanoenergetics in Mouse Myocardium
Authors: Palmer Bradley M. , Noguchi Teruo , Wang Yuan , Heim John R. , Alpert Norman R. , Burgon Patrick G. , Seidman Christine E. , Seidman J.G. , Maughan David W. , LeWinter Martin M.
Published: May 2004

We examined the effect of cardiac myosin binding protein-C (cMyBP-C) on contractile efficiency in isovolumically contracting left ventricle (LV) and on internal viscosity and oscillatory work production in skinned myocardial strips. A 6-week diet of 0.15% 6-
n
-propyl-2-thiouracil (PTU) was fed to wild-type (+/+
PTU
) and homozygous-truncated cMyBP-C (t/t
PTU
) mice starting at age ≈8 weeks and leading to a myosin heavy chain (MHC) isoform profile of 10% α-MHC and 90% β-MHC in both groups. Western blot analysis confirmed that cMyBP-C was present in the +/+
PTU
and effectively absent in the t/t
PTU
. Total LV mechanical energy per beat was quantified as pressure-volume area (PVA). O
2
consumption (Vo
2
) per beat was plotted against PVA at varying LV volumes. The reciprocal of the slope of the linear Vo
2
-PVA relation represents the contractile efficiency of converting O
2
to mechanical energy. Contractile efficiency was significantly enhanced in t/t
PTU
(26.1±2.6%) compared with +/+
PTU
(17.1±1.6%). In skinned myocardial strips, maximum isometric tension was similar in t/t
PTU
(18.7±2.1 mN · mm
−2
) and +/+
PTU
(21.9±4.0 mN · mm
−2
), but maximum oscillatory work induced by sinusoidal length perturbations occurred at higher frequencies in t/t
PTU
(7.31±1.17 Hz) compared with +/+
PTU
(4.48±0.60 Hz) and was significantly more sensitive to phosphate concentration in the t/t
PTU
. Under rigor conditions, the internal viscous load was significantly lower in the t/t
PTU
compared with +/+
PTU
, ie, ≈40% lower at 1 Hz. These results collectively suggest that contractile efficiency is enhanced in the t/t
PTU
, probably through a reduced loss of mechanical energy by a viscous load normally provided by cMyBP-C and through a gain of phosphate-dependent oscillatory work normally inhibited by cMyBP-C.
Angiogenesis Inhibitor, TNP-470, Prevents Diet-Induced and Genetic Obesity in Mice
Authors: Bråkenhielm Ebba , Cao Renhai , Gao Bihu , Angelin Bo , Cannon Barbara , Parini Paolo , Cao Yihai
Published: May 2004

Adipose tissue growth has been proposed to involve recruitment of new blood vessels. Here, we test the hypothesis that delivery of an angiogenesis inhibitor in mice may prevent diet-induced obesity, the most common type of obesity in humans. We show that systemic administration of a selective angiogenesis inhibitor, TNP-470 (AGM-1470), prevents obesity in high caloric diet-fed
wt
mice as well as in genetically leptin-deficient
ob/ob
mice. Inhibition of obesity in mice by TNP-470 involves a reduction of vascularity in the adipose tissue. This therapeutic strategy appears to selectively affect the growth of adipose tissue as measured by the ratio between total fat and lean body mass. Interestingly, the treatment with TNP-470 results in decreased serum levels of low-density lipoprotein cholesterol. Furthermore, insulin levels are reduced, which indicates increased insulin sensitivity, suggesting that angiogenesis inhibitors may prevent the development of type II diabetes. Our findings suggest that similarly to growth and organogenesis in other tissues, adipose tissue growth is dependent on angiogenesis. Our observations may have conceptual implications for the prevention of obesity and related disorders.
Effects of Electrical Shocks on Ca
i
2+
and V
m
in Myocyte Cultures
Authors: Fast Vladimir G. , Cheek Eric R. , Pollard Andrew E. , Ideker Raymond E.
Published: May 2004

Changes in intracellular calcium concentration (ΔCa
i
2+
) induced by electrical shocks may play an important role in defibrillation, but high-resolution ΔCa
i
2+
measurements in a multicellular cardiac tissue and their relationship to corresponding V
m
changes (ΔV
m
) are lacking. Here, we measured shock-induced ΔCa
i
2+
and ΔV
m
in geometrically defined myocyte cultures. Cell strands (width=0.8 mm) were double-stained with V
m
-sensitive dye RH-237 and a low-affinity Ca
i
2+
-sensitive dye Fluo-4FF. Shocks (E≈5 to 40 V/cm) were applied during the action potential plateau. Shocks caused transient Ca
i
2+
decrease at sites of both negative and positive ΔV
m
. Similar Ca
i
2+
changes were observed in an ionic model of adult rat myocytes. Simulations showed that the Ca
i
2+
decrease at sites of ΔV
+
m
was caused by the outward flow of I
CaL
and troponin binding; at sites of ΔV
−
m
it was caused by inactivation of I
CaL
combined with extrusion by Na–Ca exchanger and troponin binding. The important role of I
CaL
was supported by experiments in which application of nifedipine eliminated Ca
i
2+
decrease at ΔV
+
m
sites. Largest ΔCa
i
2+
were observed during shocks of ≈10 V/cm causing simple monophasic ΔV
m
. Shocks stronger than ≈20 V/cm caused smaller ΔCa
i
2+
and postshock elevation of diastolic Ca
i
2+
. This was paralleled with occurrence of biphasic negative ΔV
m
that indicated membrane electroporation. Thus, these data indicate that shocks transiently decrease Ca
i
2+
at sites of both ΔV
−
m
and ΔV
+
m
. Outward flow of I
CaL
plays an important role in Ca
i
2+
decrease in the ΔV
+
m
areas. Very strong shocks caused smaller negative ΔCa
i
2+
and postshock elevation of diastolic Ca
i
2+
, likely caused by membrane electroporation.
Cerebral Neutrophil Recruitment, Histology, and Outcome in Acute Ischemic Stroke
Authors: Price C.J. S. , Menon D.K. , Peters A.M. , Ballinger J.R. , Barber R.W. , Balan K.K. , Lynch A. , Xuereb J.H. , Fryer T. , Guadagno J.V. , Warburton E.A.
Published: May 2004

Background and Purpose—

Evidence now exists for a pathogenic role for neutrophils in acute cerebral ischemia. We have studied the patterns and temporal profile of cerebral neutrophil recruitment to areas of acute ischemic stroke (IS) and have attempted to correlate this with neurological status and outcome.

Methods—

Patients with cortical middle cerebral artery (MCA) IS were recruited within 24 hours of clinical onset. Neutrophil recruitment was studied using indium-111 (
111
In) troponolate-labeled neutrophils, planar imaging, and single-photon emission computed tomography (SPECT). Volume of brain infarction was calculated from concurrent computed tomography (CT). Hematoxylin and eosin sections were obtained postmortem (n=2). Outcome was measured using Barthel, Rankin, and National Institute of Health Stroke (NIHSS) scales.

Results—

Fifteen patients were studied. Significant
111
In–neutrophil recruitment to ipsilateral hemisphere, as measured by asymmetry index (AI), was demonstrated within 24 hours of onset in 9 patients; this response was heterogenous between patients and on repeated measurement attenuated over time. Histologically, recruitment was confirmed within intravascular, intramural, and intraparenchymal compartments. Interindividual heterogeneity in neutrophil response did not correlate with infarct volume or outcome. In an exploratory analysis, neutrophil accumulation appeared to correlate significantly with infarct expansion (Spearman rho=0.66;
P
=0.03, n=12).

Conclusions—

Neutrophils recruit to areas of ischemic brain within 24 hours of symptom onset. This recruitment attenuates over time and is confirmed histologically. While neutrophil accumulation may be associated with either the magnitude or the rate of infarct growth, these results require confirmation in future studies.