bluuebunny/crossref_metadata_2025 huggingface dataset:
Postfatigue potentiation of the paralyzed soleus muscle: evidence for adaptation with long-term electrical stimulation training
Authors: Shields Richard K. , Dudley-Javoroski Shauna , Littmann Andrew E.
Published: March 2006

Understanding the torque output behavior of paralyzed muscle has important implications for the use of functional neuromuscular electrical stimulation systems. Postfatigue potentiation is an augmentation of peak muscle torque during repetitive activation after a fatigue protocol. The purposes of this study were 1) to quantify postfatigue potentiation in the acutely and chronically paralyzed soleus and 2) to determine the effect of long-term soleus electrical stimulation training on the potentiation characteristics of recently paralyzed soleus muscle. Five subjects with chronic paralysis (>2 yr) demonstrated significant postfatigue potentiation during a repetitive soleus activation protocol that induced low-frequency fatigue. Ten subjects with acute paralysis (<6 mo) demonstrated no torque potentiation in response to repetitive stimulation. Seven of these acute subjects completed 2 yr of home-based isometric soleus electrical stimulation training of one limb (compliance = 83%; 8,300 contractions/wk). With the early implementation of electrically stimulated training, potentiation characteristics of trained soleus muscles were preserved as in the acute postinjury state. In contrast, untrained limbs showed marked postfatigue potentiation at 2 yr after spinal cord injury (SCI). A single acute SCI subject who was followed longitudinally developed potentiation characteristics very similar to the untrained limbs of the training subjects. The results of the present investigation support that postfatigue potentiation is a characteristic of fast-fatigable muscle and can be prevented by timely neuromuscular electrical stimulation training. Potentiation is an important consideration in the design of functional electrical stimulation control systems for people with SCI.
Expiratory threshold loading impairs cardiovascular function in health and chronic heart failure during submaximal exercise
Authors: Miller Jordan D. , Hemauer Sarah J. , Smith Curtis A. , Stickland Michael K. , Dempsey Jerome A.
Published: March 2006

We determined the effects of augmented expiratory intrathoracic pressure (PITP) production on cardiac output (QTOT) and blood flow distribution in healthy dogs and dogs with chronic heart failure (CHF). From a control expiratory PITP excursion of 7 ± 2 cmH2O, the application of 5, 10, or 15 cmH2O expiratory threshold loads increased the expiratory PITP excursion by 47 ± 23, 67 ± 32, and 118 ± 18% ( P < 0.05 for all). Stroke volume (SV) rapidly decreased (onset <10 s) with increases in the expiratory PITP excursion (−2.1 ± 0.5%, −2.4 ± 0.9%, and −3.6 ± 0.7%, P < 0.05), with slightly smaller reductions in QTOT (0.8 ± 0.6, 1.0 ± 1.1, and 1.8 ± 0.8%, P < 0.05) owing to small increases in heart rate. Both QTOT and SV were restored to control levels when the inspiratory PITP excursion was augmented by the addition of an inspiratory resistive load during 15 cmH2O expiratory threshold loading. The highest level of expiratory loading significantly reduced hindlimb blood flow by −5 ± 2% owing to significant reductions in vascular conductance (−7 ± 2%). After the induction of CHF by 6 wk of rapid cardiac pacing at 210 beats/min, the expiratory PITP excursions during nonloaded breathing were not significantly changed (8 ± 2 cmH2O), and the application of 5, 10, and 15 cmH2O expiratory threshold loads increased the expiratory PITP excursion by 15 ± 7, 23 ± 7, and 31 ± 7%, respectively ( P < 0.05 for all). Both 10 and 15 cmH2O expiratory threshold loads significantly reduced SV (−3.5 ± 0.7 and −4.2 ± 0.7%, respectively) and QTOT (−1.7 ± 0.4 and −2.5 ± 0.4%, P < 0.05) after the induction of CHF, with the reductions in SV predominantly occurring during inspiration. However, the augmentation of the inspiratory PITP excursion now elicited further decreases in SV and QTOT. Only the highest level of expiratory loading significantly reduced hindlimb blood flow (−4 ± 2%) as a result of significant reductions in vascular conductance (−5 ± 2%). We conclude that increases in expiratory PITP production-similar to those observed during severe expiratory flow limitation-reduce cardiac output and hindlimb blood flow during submaximal exercise in health and CHF.
Effects of darbepoetin injections on erythrocyte membrane transport protein expressions in humans
Authors: Rentsch Rikke Louise , Damsgaard Rasmus , Lundby Carsten , Juel Carsten
Published: March 2006

The present study investigated the effects of injected darbepoetin [novel erythropoietin stimulating protein (NESP)] on the density of three erythrocyte membrane transport proteins: the lactate-H+ cotransporter (monocarboxylate transporter 1), the chloride/bicarbonate exchanger 1 (anion exchanger 1), and the water channel aquaporin 1. Thirteen subjects were injected with NESP once a week for 4 wk. Blood samples were obtained before, during, and after the injection period, and the erythrocyte transport proteins were determined by Western blotting. The NESP injections induced a transient increase in hematocrit, red cell volume, and reticulocyte fraction. The density of aquaporin 1 protein was higher (maximal increase +59%) ( P < 0.01) during the injection period compared with the preinjection value and lower ( P < 0.01) after the injection period. The density of anion exchanger 1 protein was higher (maximal increase +15%) ( P < 0.05) during the injection period compared with the preinjection value and tended ( P = 0.06) to be lower after the injection period than before the injection period. The density of the erythrocyte monocarboxylate transporter 1 protein was higher (maximal increase +43%) ( P < 0.05) during the injection period than in the preinjection period. Age separation experiments using self-creating Percoll gradients demonstrated a higher density of membrane transport proteins in young red blood cells. These data suggest that the NESP-induced increase in membrane transport proteins is caused by a higher fraction of newly formed erythrocytes (and reticulocytes), which have a higher density of membrane transport proteins. However, increased incorporation of membrane proteins during erythrocyte formation may also be involved. We suggest that NESP improves the quality of erythrocyte membrane transport through these mechanisms.
Effects of changes in central blood volume on carotid-vasomotor baroreflex sensitivity at rest and during exercise
Authors: Ogoh Shigehiko , Brothers R. Matthew , Barnes Quinton , Eubank Wendy L. , Hawkins Megan N. , Purkayastha Sushmita , O-Yurvati Albert , Raven Peter B.
Published: March 2006

The purpose of this investigation was to examine whether the effect of changes in central blood volume on carotid-vasomotor baroreflex sensitivity at rest was the same during exercise. Eight men (means ± SE: age 26 ± 1 yr; height 180 ± 3 cm; weight 86 ± 6 kg) participated in the present study. Sixteen Torr of lower body negative pressure (LBNP) were applied to decrease central venous pressure (CVP) at rest and during steady-state leg cycling at 50% peak O2 uptake (104 ± 20 W). Subsequently, infusions of 25% human serum albumin solution were administered to increase CVP at rest and during exercise. During all protocols, heart rate, arterial blood pressure, and CVP were recorded continuously. At each stage of LBNP or albumin infusion, the maximal gain (Gmax) of the carotid-vasomotor baroreflex function curve was measured using the neck pressure and neck suction technique. LBNP reduced CVP and increased the Gmax of the carotid-vasomotor baroreflex function curve at rest (+63 ± 25%, P = 0.006) and during exercise (+69 ± 19%, P = 0.002). In contrast to the LBNP, increases in CVP resulted in the Gmax of the carotid-vasomotor baroreflex function curve being decreased at rest −8 ± 4% and during exercise −18 ± 5% ( P > 0.05). These findings indicate that the relationship between CVP and carotid-vasomotor baroreflex sensitivity was nonlinear at rest and during exercise and suggests a saturation load of the cardiopulmonary baroreceptors at which carotid-vasomotor baroreflex sensitivity remains unchanged.
Increases in lung expansion alter pulmonary hemodynamics in fetal sheep
Authors: Polglase Graeme R. , Wallace Megan J. , Morgan David L. , Hooper Stuart B.
Published: March 2006

Prolonged increases in fetal lung expansion stimulate fetal lung growth and development, but the effects on pulmonary hemodynamics are unknown. Our aim was to determine the effect of increased fetal lung expansion, induced by tracheal obstruction (TO), on pulmonary blood flow (PBF) and vascular resistance (PVR). Chronically catheterized fetal sheep ( n = 6) underwent TO from 120 to 127 days of gestational age (term ∼147 days); tracheas were not obstructed in control fetuses ( n = 6). PBF, PVR, and changes to the PBF waveform were determined. TO significantly increased lung wet weight compared with control (166.3 ± 20.2 vs. 102.0 ± 18.8 g; P < 0.05). Despite the increase in intraluminal pressure caused by TO (5.0 ± 0.9 vs. 2.4 ± 1.0 mmHg; P < 0.001), PBF and PVR were similar between groups after 7 days (TO 28.1 ± 3.2 vs. control 34.1 ± 10.0 ml·min−1·100 g lung wt−1). However, TO markedly altered pulmonary hemodynamics associated with accentuated fetal breathing movements, causing a reduction rather than an increase in PBF at 7 days of TO. To account for the increase in intraluminal pressure, the pressure was equalized by draining the lungs of liquid on day 7 of TO. Pressure equalization increased PBF from 36.8 ± 5.2 to 112.4 ± 22.8 ml/min ( P = 0.01) and markedly altered the PBF waveform. These studies provide further evidence to indicate that intraluminal pressure is an important determinant of PBF and PVR in the fetus. We suggest that the increase in PBF associated with pressure equalization following TO reflects an increase in growth of the pulmonary vascular bed, leading to an increase in its cross-sectional area.
Acute effects of thixotropy conditioning of inspiratory muscles on end-expiratory chest wall and lung volumes in normal humans
Authors: Izumizaki Masahiko , Iwase Michiko , Ohshima Yasuyoshi , Homma Ikuo
Published: March 2006

Thixotropy conditioning of inspiratory muscles consisting of maximal inspiratory effort performed at an inflated lung volume is followed by an increase in end-expiratory position of the rib cage in normal human subjects. When performed at a deflated lung volume, conditioning is followed by a reduction in end-expiratory position. The present study was performed to determine whether changes in end-expiratory chest wall and lung volumes occur after thixotropy conditioning. We first examined the acute effects of conditioning on chest wall volume during subsequent five-breath cycles using respiratory inductive plethysmography ( n = 8). End-expiratory chest wall volume increased after conditioning at an inflated lung volume ( P < 0.05), which was attained mainly by rib cage movements. Conditioning at a deflated lung volume was followed by reductions in end-expiratory chest wall volume, which was explained by rib cage and abdominal volume changes ( P < 0.05). End-expiratory esophageal pressure decreased and increased after conditioning at inflated and deflated lung volumes, respectively ( n = 3). These changes in end-expiratory volumes and esophageal pressure were greatest for the first breath after conditioning. We also found that an increase in spirometrically determined inspiratory capacity ( n = 13) was maintained for 3 min after conditioning at a deflated lung volume, and a decrease for 1 min after conditioning at an inflated lung volume. Helium-dilution end-expiratory lung volume increased and decreased after conditioning at inflated and deflated lung volumes, respectively (both P < 0.05; n = 11). These results suggest that thixotropy conditioning changes end-expiratory volume of the chest wall and lung in normal human subjects.
Activation Antigens during the Proliferative and Secretory Phases of Endometrium and Early-Pregnancy Decidua
Authors: Ugur Yesim , Cakar A. Nur , Beksac M. Sinan , Dagdeviren Attila
Published: March 2006

Background: Clarifying the normal distribution of activation antigens will contribute to database construction studies of monoclonal-antibody-based therapies in endometrial disorders. Methods: In this study, endometrial tissue samples obtained during proliferative and secretory phases and decidual samples of early pregnancies were immunostained by the monoclonal antibodies anti-CD26, anti-CD30, anti-CD70, anti-CD71, and anti-CD98 using the indirect immunoperoxidase method. Results: CD26 is expressed on the glandular epithelium in the endometrium and decidua. Endothelial CD26 is expressed less in the decidua when compared to the endometrium. CD30 is strongly expressed by decidual cells. It is only weakly expressed on endometrial and decidual vessels. Glandular and endothelial CD70 expression is mainly seen in the proliferative phase of the menstrual cycle. Glandular CD71 expression is less in the decidua when compared to the endometrium. Its expression on stromal cells is more in the secretory phase of the menstrual cycle and in early pregnancy deciduae. It is expressed on endometrial vessels but not on decidual vessels. Glandular CD98 is expressed more in the decidua when compared to the endometrium. This antigen exists on endometrial lymphocytes. It is strongly expressed on the endothelium in the endometrium and decidua. Conclusion: It seems that CD26 and CD70 are not involved in the functions of endometrial and decidual stromal cells. CD30 and CD71 are thought to be involved in decidualization. Absence of activation antigens other than CD98 on lymphocytes indicated an antigenic profile for large granular lymphocytes that is different from regular lymphocytes.
MMP-9 Microsatellite Polymorphism and Susceptibility to Carotid Arteries Atherosclerosis
Authors: Fiotti Nicola , Altamura Nicola , Fisicaro Maurizio , Carraro Nicola , Uxa Laura , Grassi Gabriele , Torelli Lucio , Gobbato Raffaella , Guarnieri Gianfranco , Baxter B. Timothy , Giansante Carlo
Published: March 2006

Objective—

The aims of this study were to compare a microsatellite polymorphism (PM) of matrix metalloproteinase (MMP)-9 in patients with carotid atherosclerosis and control population, and to assess the relationship between this PM and plaque structure.

Methods and Results—

One hundred fifty patients referring to vascular diagnostic centers for suspected carotid atherosclerosis (at ultrasound examination: 110 positive, 40 negative) and controls (n=110) have been genotyped for MMP-9 PM. After controlling for risk factors, allelic and genotype frequencies were significantly different among the groups, with significant prevalence of long microsatellites in patients with carotid atherosclerosis. Long microsatellites (settled as 22 to 27 repeats) were associated with carotid atherosclerosis (odds ratio [OR], 5.2; 95% confidence interval [CI], 2.9 to 9.2), compared with controls; an independent case control study on patients with coronary atherosclerosis confirmed such result. Binary logistic regression showed that hypertension, long microsatellites in MMP-9 PM and smoking habits were variables accounting for the difference between ultrasound-positive patients and controls. Long microsatellites were also associated to plaques with thin fibrous cap and echolucent core (OR, 13.1; 95% CI, 1.6 to 100). These alleles were slightly more represented in female patients (χ
2
test=0.019; OR, 2.7; 95% CI, 1.2 to 6) but not associated with other risk factors. Plasma MMP-9 levels were related neither to MMP-9 PM nor to plaque type, and were related to gender and extension of atherosclerosis in carotid arteries.

Conclusions—

The number of repeats (≥22 CA) in the microsatellite of MMP-9 promoter, but not MMP-9 plasma levels, is associated to carotid atherosclerosis and particularly to plaques with a thin fibrous cap.
Hypercholesterolemia Reduces Collateral Artery Growth More Dominantly Than Hyperglycemia or Insulin Resistance in Mice
Authors: van Weel Vincent , de Vries Margreet , Voshol Peter J. , Verloop Robert E. , Eilers Paul H.C. , van Hinsbergh Victor W.M. , van Bockel J. Hajo , Quax Paul H.A.
Published: March 2006

Objective—

Collateral artery development (arteriogenesis), a vital compensatory mechanism in patients with arterial obstructive disease, may be deregulated by vascular risk factors, eg, diabetes or hypercholesterolemia. Here, we compared the effects of either disturbed glucose metabolism or disturbed lipid metabolism on arteriogenesis.

Methods and Results—

Femoral artery occlusion was performed in streptozotocin(STZ)-treated mice, nonobese diabetic (NOD) mice, and insulin-resistant Ob/Ob mice on regular diet, and APOE3*Leiden mice on different hypercholesterolemic diets. Angiography and laser Doppler perfusion analysis of hindlimbs were performed postoperatively. Surprisingly, angiographic arteriogenesis was not impaired in diabetic and insulin-resistant mice. Perfusion recovery in STZ-treated and Ob/Ob mice was only decreased by 19% and 16%, respectively (
P
<0.05). Furthermore, perfusion recovery was unchanged between high-glycemic and mild-glycemic NOD mice. Angiographic arteriogenesis in APOE3*Leiden mice, however, was markedly impaired at 7 days and 14 days (
P
≤0.01). Correspondingly, perfusion recovery was 41% decreased in APOE3*Leiden mice (
P
<0.05). There was an inverse correlation of perfusion recovery with plasma cholesterol (
P
=0.02), but not with triglyceride, free fatty acid, glucose, or insulin levels.

Conclusions—

Hypercholesterolemia reduces arteriogenesis more dominantly than hyperglycemia or hyperinsulinemia in mice. This suggests that a disturbed lipid metabolism as observed in diabetic patients might be crucial for the impairment of collateral formation.
Genome-Wide Expression Studies of Atherosclerosis
Authors: Bijnens A.P.J.J. , Lutgens E. , Ayoubi T. , Kuiper J. , Horrevoets A.J. , Daemen M.J.A.P.
Published: March 2006

During the past 6 years, gene expression profiling of atherosclerosis has been used to identify genes and pathways relevant in vascular (patho)physiology. This review discusses some critical issues in the methodology, analysis, and interpretation of the data of gene expression studies that have made use of vascular specimens from animal models and humans. Analysis of gene expression studies has evolved toward the genome-wide expression profiling of large series of individual samples of well-characterized donors. Despite the advances in statistical and bioinformatical analysis of expression data sets, studies have not yet fully exploited the potential of gene expression data sets to obtain novel insights into the molecular mechanisms underlying atherosclerosis. To assess the potential of published expression data, we compared the data of a CC chemokine gene cluster between 18 murine and human gene expression profiling articles. Our analysis revealed that an adequate comparison is mainly hindered by the incompleteness of available data sets. The challenge for future vascular genomic profiling studies will be to further improve the experimental design, statistical, and bioinformatical analysis and to make data sets freely accessible.
Adiponectin Is an Important Determinant of ApoA-I Catabolism
Authors: Vergès Bruno , Petit Jean Michel , Duvillard Laurence , Dautin Guillaume , Florentin Emmanuel , Galland Françoise , Gambert Philippe
Published: March 2006

Objective—

Plasma concentration of adiponectin is positively correlated with high-density lipoprotein (HDL) cholesterol level. However, the role of adiponectin on HDL metabolism remains unknown. This prompted us to perform an in vivo kinetic study of apoA-I, the main apolipoprotein of HDL, using stable isotopes, in 22 subjects with a wide range of plasma adiponectin, including 11 patients with metabolic syndrome (8 with type 2 diabetes, 3 without type 2 diabetes) and 11 normal individuals.

Methods and Results—

In the 22 studied subjects, plasma adiponectin levels ranged from 2.57 to 14.44 μg/mL and apoA-I fractional catabolic rate (FCR) values ranged from 0.142 to 0.340 day
−1
. A strong negative correlation was found between adiponectin and apoA-I FCR (
r
=−0.66,
P
<0.001) in the whole studied population and, to a similar extent, in patients with metabolic syndrome (
r
=−0.73,
P
=0.010) and normal subjects (
r
=−0.68,
P
=0.020), separately. In multivariable analysis, apoA-I FCR was associated negatively with adiponectin (
P
=0.005) and positively with HDL triglycerides/cholesterol ratio (
P
=0.006), but not with age, sex, body mass index (BMI), waist circumference, plasma triglycerides, HDL cholesterol, fasting glycemia, and QUICKI. Both adiponectin and HDL triglycerides/cholesterol ratio explained 62% of the variance of apoA-I FCR and adiponectin on its own explained 43%.

Conclusions—

Our kinetic study shows a strong negative correlation between adiponectin and apoA-I FCR, which can explain the positive link between HDL cholesterol and adiponectin. This association is independent of obesity, insulin resistance, and the content of triglycerides within HDL particles. These data suggest that adiponectin may have a direct role on HDL catabolism.
Plasma Homocysteine Affects Fibrin Clot Permeability and Resistance to Lysis in Human Subjects
Authors: Undas Anetta , Brożek Jan , Jankowski Miłosz , Siudak Zbigniew , Szczeklik Andrew , Jakubowski Hieronim
Published: March 2006

Objective—Homocysteine (Hcy) is a risk factor for thrombosis. We investigated a hypothesis that the clot permeability and its resistance to fibrinolysis is associated with plasma total Hcy (tHcy) in human subjects.

Methods and Results—We studied healthy men not taking any medication (n=76), male patients with advanced coronary artery disease (CAD) taking low-dose aspirin (n=33), men with diabetes mellitus diagnosed recently (median hemoglobin A1c7.65%; n=16), and patients with isolated hypercholesterolemia (>7.0 mmol/L; n=15). We assessed clot permeability and turbidimetric lysis time as the determinants of fibrin clot structure. In a regression model, including age and fibrinogen, plasma tHcy was an independent predictor of clot permeation and fibrinolysis time in healthy subjects (R2=0.88,P<0.0001 andR2=0.54,P<0.0001, respectively). In CAD patients, tHcy and fibrinogen were stronger predictors of the permeation coefficient (R2=0.84;P<0.0001) than was fibrinogen alone (R2=0.66;P<0.0001), whereas tHcy was the only predictor of lysis time (R2=0.69;P<0.0001). Elevated tHcy levels observed after methionine load were not associated with any of the fibrin clot properties. In patients with diabetes or hypercholesterolemia, the influence of Hcy on permeation and, to a lesser extent, on the lysis time was obscured by dominant effects of glucose and cholesterol. In 20 asymptomatic men with hyperhomocysteinemia treated with folic acid, reduction in tHcy levels resulted in increased clot permeability (P=0.0002) and shorter lysis time (P<0.0001).

Conclusions—Our results indicate that plasma tHcy predicts clot permeation and susceptibility to fibrinolysis in healthy men and CAD patients. Our data are consistent with a mechanism of thrombosis in hyperhomocysteinemia, which involves modification of fibrinogen by Hcy–thiolactone.
Biological Significance of Decreased HSP27 in Human Atherosclerosis
Authors: Martin-Ventura Jose Luis , Nicolas Valentin , Houard Xavier , Blanco-Colio Luis Miguel , Leclercq Anne , Egido Jesús , Vranckx Roger , Michel Jean-Baptiste , Meilhac Olivier
Published: March 2006

Objective—

Because culprit atherosclerotic plaques contain proteases, we hypothesized that the diminished heat shock protein 27 (HSP27) released by atherosclerotic plaques could be due to proteolysis. We assessed the role of HSP27 in human vascular smooth muscle cells (VSMCs) under proteolytic injury.

Methods and Results—

Active plasmin is present in culprit atherosclerotic plaques. Recombinant HSP27 was cleaved by plasmin and this effect was prevented by different inhibitors. Fragments and aggregated forms of HSP27 appeared after incubation of mammary control endarteries with plasmin. Coincubation of atherosclerotic plaques with recombinant HSP27 or mammary endarteries led to HSP27 proteolysis. After incubation of VSMCs with plasmin, HSP27 was overexpressed, phosphorylated, aggregated, and redistributed from the cytoskeleton to the cytosol, nucleus, and cell membrane. Plasmin-induced VSMC apoptosis was significantly higher in VSMCs treated by HSP27 siRNA. Immunohistochemical analysis of atherosclerotic plaques showed that plasmin(ogen) and apoptotic cells are localized in the core/shoulder whereas HSP27 and VSMCs are mainly expressed in the cap/media.

Conclusions—

Extracellular HSP27 can be degraded by enzymes released from atherosclerotic plaques and may reflect a proteolytic imbalance. Intracellular HSP27 downregulation decreases VSMCs resistance to proteolytically-induced apoptosis. HSP27 might play a pivotal role in the prevention of plaque instability and rupture.
Scavenger Receptor BI Prevents Nitric Oxide–Induced Cytotoxicity and Endotoxin-Induced Death
Authors: Li Xiang-An , Guo Ling , Asmis Reto , Nikolova-Karakashian Mariana , Smart Eric J.
Published: March 2006

Nitric oxide (NO)-induced oxidative stress contributes to a variety of diseases. Although numerous mechanisms have been described controlling the production of NO, the mechanisms to prevent NO-induced cytotoxicity after NO synthesis are largely unknown. Here we report that scavenger receptor BI (SR-BI) prevents NO-induced cytotoxicity. Using CHO cell lines expressing wild-type and single-site mutant SR-BI protein, we demonstrate that SR-BI prevents NO-induced cytotoxicity and that a highly conserved CXXS redox motif is required for the anti-NO cytotoxicity activity of SR-BI. Using genetically manipulated mice, we demonstrate that SR-BI–null mice have a 3- to 4-fold increase in tyrosine nitrated proteins in aorta and liver compared with wild-type littermates, indicating that expression of SR-BI prevents peroxynitrite formation in vivo. Using lipopolysacharide (LPS)-challenged mice as an in vivo model of NO-induced cytotoxicity, we found that a single dose of LPS (120 000 U/g IP) induced 90% fatality of SR-BI–null mice within 3 days, whereas all of the wild-type littermates survived (n=20), demonstrating that SR-BI is highly protective against NO cytotoxicity in vivo. Importantly, SR-BI prevents LPS-induced death without eliminating NO production, suggesting that SR-BI prevents NO-induced cytotoxicity post-NO synthesis. Our study describes a novel observation that may shed new light on the treatment of nitric oxidative stress–associated diseases, such as septic shock.
Endostatin, the Proteolytic Fragment of Collagen XVIII, Induces Vasorelaxation
Authors: Wenzel D. , Schmidt A. , Reimann K. , Hescheler J. , Pfitzer G. , Bloch W. , Fleischmann B.K.
Published: March 2006

Collagen XVIII is an important component of the extracellular matrix and is expressed in basement membranes. Its degradation results in the generation of endostatin claimed to possess antiangiogenic activity. To date, only limited knowledge exists with regard to the cellular signaling of this molecule. We show in single-cell measurements using the Ca
2+
indicator fura-2 acetoxy methylester (fura-2 AM) and the nitric oxide (NO) indicator 4,5-diaminofluorescein diacetate that application of endostatin (ES) (5 pmol/L, 100 ng/mL) induced Ca
2+
spikes and an increase of NO production in human and murine endothelial cells. The NO response was independent of an increase in cytosolic Ca
2+
and blocked by the endothelial NO synthase (eNOS) inhibitor
N
G
-nitro-
l
-arginine methyl ester and by incubation with pertussis toxin known to inhibit G
i/o
proteins. The physiological relevance of this novel signaling pathway of ES was assessed with isometric force measurements in large and small arteries of mouse. Physiological concentrations of ES were found to decrease vascular tone in an endothelium-dependent manner. This occurred via an Arg-Gly-Asp (RGD) peptide–independent pathway through activation of G
i/o
proteins, phosphatidylinositol 3-kinase, Akt, and eNOS. We conclude that the proteolytic matrix fragment ES is a prominent vasorelaxing agent. Because ES is constantly released into the blood, it is a novel regulator of blood pressure and, therefore, represents an interesting pharmacological target.
Critical Roles of Muscle-Secreted Angiogenic Factors in Therapeutic Neovascularization
Authors: Tateno Kaoru , Minamino Tohru , Toko Haruhiro , Akazawa Hiroshi , Shimizu Naomi , Takeda Shinichi , Kunieda Takeshige , Miyauchi Hideyuki , Oyama Tomomi , Matsuura Katsuhisa , Nishi Jun-ichiro , Kobayashi Yoshio , Nagai Toshio , Kuwabara Yoichi , Iwakura Yoichiro , Nomura Fumio , Saito Yasushi , Komuro Issei
Published: March 2006

The discovery of bone marrow–derived endothelial progenitors in the peripheral blood has promoted intensive studies on the potential of cell therapy for various human diseases. Accumulating evidence has suggested that implantation of bone marrow mononuclear cells effectively promotes neovascularization in ischemic tissues. It has also been reported that the implanted cells are incorporated not only into the newly formed vessels but also secrete angiogenic factors. However, the mechanism by which cell therapy improves tissue ischemia remains obscure. We enrolled 29 “no-option” patients with critical limb ischemia and treated ischemic limbs by implantation of peripheral mononuclear cells. Cell therapy using peripheral mononuclear cells was very effective for the treatment of limb ischemia, and its efficacy was associated with increases in the plasma levels of angiogenic factors, in particular interleukin-1β (IL-1β). We then examined an experimental model of limb ischemia using IL-1β–deficient mice. Implantation of IL-1β–deficient mononuclear cells improved tissue ischemia as efficiently as that of wild-type cells. Both wild-type and IL-1β–deficient mononuclear cells increased expression of IL-1β and thus induced angiogenic factors in muscle cells of ischemic limbs to a similar extent. In contrast, inability of muscle cells to secrete IL-1β markedly reduces induction of angiogenic factors and impairs neovascularization by cell implantation. Implanted cells do not secret angiogenic factors sufficient for neovascularization but, instead, stimulate muscle cells to produce angiogenic factors, thereby promoting neovascularization in ischemic tissues. Further studies will allow us to develop more effective treatments for ischemic vascular disease.
Urocortin-Induced Decrease in Ca
2+
Sensitivity of Contraction in Mouse Tail Arteries Is Attributable to cAMP-Dependent Dephosphorylation of MYPT1 and Activation of Myosin Light Chain Phosphatase
Authors: Lubomirov Lubomir T. , Reimann Katrin , Metzler Doris , Hasse Veronika , Stehle Robert , Ito Masaaki , Hartshorne David J. , Gagov Hristo , Pfitzer Gabriele , Schubert Rudolf
Published: March 2006

Urocortin, a vasodilatory peptide related to corticotropin-releasing factor, may be an endogenous regulator of blood pressure. In vitro, rat tail arteries are relaxed by urocortin by a cAMP-mediated decrease in myofilament Ca
2+
sensitivity through a still unclear mechanism. Here we show that contraction of intact mouse tail arteries induced with 42 mmol/L KCl or 0.5 μmol/L noradrenaline was associated with a ≈2-fold increase in the phosphorylation of the regulatory subunit of myosin phosphatase (SMPP-1M), MYPT1, at Thr696, which was reversed in arteries relaxed with urocortin. Submaximally (pCa 6.1) contracted mouse tail arteries permeabilized with α-toxin were relaxed with urocortin by 39±3% at constant [Ca
2+
], which was associated with a decrease in myosin light chain (MLC
20
Ser19
), MYPT1
Thr696
, and MYPT1
Thr850
phosphorylation by 60%, 28%, and 52%, respectively. The Rho-associated kinase (ROK) inhibitor Y-27632 decreased MYPT1 phosphorylation by a similar extent. Inhibition of PP-2A with 3 nmol/L okadaic acid had no effect on MYPT1 phosphorylation, whereas inhibition of PP-1 with 3 μmol/L okadaic acid prevented dephosphorylation. Urocortin increased the rate of dephosphorylation of MLC
20
Ser19
≈2.2-fold but had no effect on the rate of contraction under conditions of, respectively, inhibited kinase and phosphatase activities. The effect of urocortin on MLC
20
Ser19
and MYPT1 phosphorylation was blocked by Rp-8-CPT-cAMPS and mimicked by Sp-5,6-DCl-cBIMPS. In summary, these results provide evidence that Ca
2+
-independent relaxation by urocortin can be attributed to a cAMP-mediated increased activity of SMPP-1M which at least in part is attributable to a decrease in the inhibitory phosphorylation of MYPT1.
Absence of TRAM Restricts Toll-Like Receptor 4 Signaling in Vascular Endothelial Cells to the MyD88 Pathway
Authors: Harari Olivier A. , Alcaide Pilar , Ahl Daniela , Luscinskas F. William , Liao James K.
Published: March 2006

Mammalian cells respond to bacterial lipopolysaccharide (LPS) through a cognate receptor: Toll-like receptor 4 (TLR4). The signaling pathways, which link TLR4 to the proinflammatory transcription factor nuclear factor κB (NF-κB), occur through the intracellular docking proteins MyD88 and Trif. We hypothesize that unlike antigen-presenting cells, vascular endothelial cells (ECs) lack the Trif protein TRAM and are therefore incapable of eliciting Trif-dependent immune responses to LPS. Stimulation of wild-type mice with LPS leads to the activation of NF-κB in ECs and macrophages in vitro and in vivo. In contrast to macrophages, LPS did not activate endothelial NF-κB or NF-κB–dependent genes in MyD88
−/−
mice, suggesting the absence of a functional Trif pathway in vascular ECs. Indeed, the Trif-dependent gene
cxcl10
was not expressed in ECs after LPS stimulation. This correlated with diminished expression of the Trif accessory TIR protein TRAM in ECs. Overexpression of TRAM cDNA in ECs reconstituted LPS-induced Trif-dependent NF-κB activation and
cxcl10
promoter activity. The functional absence of TRAM in vascular ECs restricts TLR4 signaling to MyD88-dependent pathway. This is in contrast to macrophages, which respond to LPS via both Trif- and MyD88-dependent pathways. These findings indicate that vascular ECs do not express the Trif-dependent gene subset. This implies that these genes may be dispensable for the endothelial response to bacterial infection and play no role in the endothelial contribution to the development of atherosclerosis.
Monocyte Chemoattractant Protein-1 Induces a Novel Transcription Factor That Causes Cardiac Myocyte Apoptosis and Ventricular Dysfunction
Authors: Zhou Limei , Azfer Asim , Niu Jianli , Graham Sarabeth , Choudhury Mahua , Adamski Frances M. , Younce Craig , Binkley Phillip F. , Kolattukudy Pappachan E.
Published: March 2006

Monocyte chemoattractant protein-1 (MCP-1; CCL2)–mediated inflammation plays a critical role in the development of ischemic heart disease (IHD). However, the gene expression changes caused by signal transduction, triggered by MCP-1 binding to its receptor CCR2, and their possible role in the development of IHD are not understood. We present evidence that MCP-1 binding to CCR2 induces a novel transcription factor (MCP-induced protein [MCPIP]) that causes cell death. Gene microarray analysis showed that when expressed in hiuman embryonic kidney 293 cells, MCPIP induced apoptotic gene families before causing cell death. Mutagenesis studies showed that the structural features required for transcription factor–like activity were also required for causing cell death. Activation of caspase-3 was detected after MCPIP transfection and Z-VAD-fmk partially inhibited cell death. Cardiomyocyte-targeted expression of MCP-1 in mice caused death by heart failure at 6 months of age. MCPIP expression increased in parallel with the development of ventricular dysfunction. In situ hybridization showed the presence of MCPIP transcripts in the cardiomyocytes and immunohistochemistry showed that MCPIP was associated with the cardiomyocyte nuclei of apoptotic cardiomyocytes. CCR2 expression in cardiomyocytes increased with the development of IHD. MCPIP production induced by MCP-1 binding to CCR2 in the cardiomyocytes is probably involved in the development of IHD in this murine model. MCPIP transcript levels were much higher in the explanted human hearts with IHD than with nonischemic heart disease. These results provide a molecular insight into how chronic inflammation and exposure to MCP-1 contributes to heart failure and suggest that MCPIP could be a potential target for therapeutic intervention.
Ischemic Thresholds for Gray and White Matter
Authors: Arakawa Shuji , Wright Peter M. , Koga Masatoshi , Phan Thanh G. , Reutens David C. , Lim Indra , Gunawan Marveyles R. , Ma Henry , Perera Nilupul , Ly John , Zavala Jorge , Fitt Gregory , Donnan Geoffery A.
Published: March 2006

Background and Purpose—

Although gray matter (GM) and white matter (WM) have differing neurochemical responses to ischemia in animal models, it is unclear whether this translates into differing thresholds for infarction. We studied this issue in ischemic stroke patients using magnetic resonance (MR) techniques.

Methods—

MR studies were performed in patients with acute hemispheric ischemic stroke occurring within 24 hours and at 3 months. Cerebral blood flow (CBF), cerebral blood volume (CBV), mean transit time (MTT), and apparent diffusion coefficient (ADC) were calculated. After segmentation based on a probabilistic map of GM and WM, tissue-specific diffusion and perfusion thresholds for infarction were established.

Results—

Twenty-one patients were studied. Infarction thresholds for CBF were significantly higher in GM (median 34.6 mL/100 g per minute, interquartile range 26.0 to 38.8) than in WM (20.8 mL/100 g per minute; interquartile range 18.0 to 25.9;
P
<0.0001). Thresholds were also significantly higher in GM than WM for CBV (GM: 1.67 mL/100 g; interquartile range 1.39 to 2.17; WM: 1.19 mL/100 g; interquartile range 0.94 to 1.53;
P
<0.0001), ADC (GM: 918×10
−6
mm
2
/s; 868 to 975×10
−6
; WM: 805×10
−6
; 747 to 870×10
−6
;
P
<0.001), and there was a trend toward a shorter MTT in GM (GM 4.94 s, 4.44 to 5.38; WM 5.15, 4.11 to 5.68;
P
=0.11).

Conclusions—

GM has a higher infarction threshold for CBF, CBV, and ADC than WM in patients within 24 hours of ischemic stroke onset. Hence, when assessing patients for potential therapies, tissue-specific rather than whole-brain thresholds may be a more precise measure of predicting the likelihood of infarction.
Deletion of Cellular Prion Protein Results in Reduced Akt Activation, Enhanced Postischemic Caspase-3 Activation, and Exacerbation of Ischemic Brain Injury
Authors: Weise Jens , Sandau Raoul , Schwarting Sönke , Crome Olaf , Wrede Arne , Schulz-Schaeffer Walter , Zerr Inga , Bähr Mathias
Published: March 2006

Background and Purpose—

The physiological function of cellular prion protein (PrP
c
) is not yet understood. Recent findings suggest that PrP
c
may have neuroprotective properties, and its absence increases susceptibility to neuronal injury. The purpose of this study was to elucidate the role of PrP
c
in ischemic brain injury in vivo.

Methods—

PrP knockout (Prnp
0/0
) and Prnp
+/+
wild-type (WT) mice were subjected to 60-minute transient or permanent focal cerebral ischemia followed by infarct volume analysis 24 hours after lesion. To identify effects of PrP
c
deletion on mechanisms regulating ischemic cell death, expression analysis of several proapoptotic and antiapoptotic proteins was performed at 6 and 24 hours after transient ischemia and in nonischemic controls using Western blot or immunohistochemistry.

Results—

Prnp
0/0
mice displayed significantly increased infarct volumes after both transient or permanent ischemia when compared with WT animals (70.2±23 versus 13.3±4 mm
3
; 119.8±24 versus 86.4±25 mm
3
). Expression of phospho-Akt (Ser473) was significantly reduced in Prnp
0/0
compared with WT animals both early after ischemia and in sham controls. Furthermore, postischemic caspase-3 activation was significantly enhanced in the basal ganglia and the parietal cortex of Prnp
0/0
mice. In contrast, expression of total Akt, Bax, and Bcl-2 did not differ between both groups.

Conclusions—

These results demonstrate that PrP
c
deletion impairs the antiapoptotic phosphatidylinositol 3-kinase/Akt pathway by resulting in reduced postischemic phospho-Akt expression, followed by enhanced postischemic caspase-3 activation, and aggravated neuronal injury after transient and permanent cerebral ischemia.
Not All Patients With Atrial Fibrillation–Associated Ischemic Stroke Can Be Started on Anticoagulant Therapy
Authors: Somerfield Jennifer , Barber P. Alan , Anderson Neil E. , Kumar Ajay , Spriggs David , Charleston Alison , Bennett Patricia , Baker Yvette , Ross Linda
Published: March 2006

Background and Purpose—

Ischemic stroke patients in atrial fibrillation (AF) have a 10% to 20% risk of recurrent stroke. Warfarin reduces this risk by two thirds. However, warfarin is underutilized in this patient group. We performed a prospective study to determine the reasons why warfarin is not started in these patients.

Methods—

All patients with AF-associated ischemic stroke over a 12-month period were identified. Demographic and other data, including whether warfarin was commenced or recommended at discharge, and if not why not, were recorded.

Results—

Ninety-three of 412 (23%) ischemic stroke patients had paroxysmal or permanent AF. Of these patients, 17 (18%) died, 48 (52%) were discharged home, and 28 (30%) were discharged to institutional care. Only 13 of 64 (20%) patients with known AF were taking warfarin at stroke onset. Warfarin was started (or recommended) in 35 of 76 (46%) survivors. Of those not commenced on warfarin, 32 (78%) were dependent (
P
<0.001) and 23 (56%) were discharged to institutional care (
P
<0.001). Warfarin was not started because of severe disability and frailty in 13 (32%), risk of falls in 12 (30%), and limited life expectancy in 4 (10%).

Conclusions—

In this cohort of patients with AF, warfarin was primarily underutilized before stroke onset, and it was too late to use anticoagulation, in approximately half, once a stroke had occurred. The decision to start or continue anticoagulation requires clinical judgment and should be made on a case by case basis after a complete risk benefit assessment.
The Influence of Hypothermia on Outcome After Intracerebral Hemorrhage in Rats
Authors: MacLellan Crystal L. , Davies Laura M. , Fingas Matthew S. , Colbourne Frederick
Published: March 2006

Background and Purpose—

Late hypothermia (HYPO) reduces injury after collagenase-induced intracerebral hemorrhage (ICH), whereas early HYPO does not because it exacerbates the protracted bleeding that occurs in this model. We hypothesized that early HYPO would not increase bleeding after whole blood infusion and thus expected early HYPO to improve outcome through reducing secondary consequences of ICH (eg, inflammation).

Methods—

Autologous blood (100 μL) was infused into the striatum. Rats were maintained at normothermia or subjected to mild (33°C to 35°C) HYPO for 2 days starting 1 (HYPO-1) or 4 hours (HYPO-4) after ICH. Hematoma volume was measured at 12 hours to determine whether HYPO-1 aggravated bleeding. We measured blood–brain barrier (BBB) disruption and edema 2 days after ICH in all groups. At 4 days, we counted degenerating neurons, neutrophils, and iron-positive cells (eg, macrophages) in the lesioned hemisphere. Recovery was assessed using several behavioral tests (ie, staircase reaching task, ladder walking task, limb use cylinder test) over 7 or 30 days, at which time we quantified lesion volume.

Results—

HYPO did not increase bleeding. Both HYPO treatments reduced BBB disruption and infiltration of inflammatory cells. HYPO-1 treatment modestly reduced edema and provided limited to no functional benefit in the behavioral tests. HYPO did not affect lesion volume.

Conclusions—

HYPO reduced edema, BBB disruption, and inflammation. Although encouraging, HYPO treatment must be improved so that histological and functional benefit are obtained before clinical investigation. Otherwise clinical failure is anticipated.
Multiple Mechanisms Underlying the Neuroprotective Effects of Antiepileptic Drugs Against In Vitro Ischemia
Authors: Costa Cinzia , Martella Giuseppina , Picconi Barbara , Prosperetti Chiara , Pisani Antonio , Di Filippo Massimiliano , Pisani Francesco , Bernardi Giorgio , Calabresi Paolo
Published: March 2006

Background and Purpose—

The possible neuroprotective effects of classic and new antiepileptic drugs on the electrophysiological changes induced by in vitro ischemia on striatal neurons were investigated. In particular, the aim of the study was to correlate the putative neuroprotective effects with the action of these drugs on fast sodium (Na
+
) and high-voltage–activated (HVA) calcium (Ca
2+
) currents.

Methods—

Extracellular field potentials were recorded from rat corticostriatal brain-slice preparations. In vitro ischemia was delivered by switching to an artificial cerebrospinal fluid solution in which glucose and oxygen were omitted. Na
+
and HVA Ca
2+
currents were analyzed by whole-cell patch-clamp recordings from acutely isolated rat striatal neurons. Excitatory postsynaptic potential was measured following synaptic stimulation in corticostriatal slices by sharp intracellular microelectrodes.

Results—

Neuroprotection against in vitro ischemia was observed in slices treated with carbamazepine (CBZ), valproic acid (VPA), and topiramate (TPM), whereas it was not achieved by using levetiracetam (LEV). Fast Na
+
conductances were inhibited by CBZ and TPM, whereas VPA and LEV showed no effect. HVA Ca
2+
conductances were reduced by CBZ, TPM, and LEV. VPA had no effect on this current. All antiepileptic drugs induced a small reduction of excitatory postsynaptic potential amplitude at concentrations higher than 100 μm without changes of paired-pulse facilitation.

Conclusions—

The concomitant inhibition of fast Na
+
and HVA Ca
2+
conductances is critically important for the neuroprotection, whereas the presynaptic inhibition on glutamate transmission does not seem to play a major role.
Patient Behavior Immediately After Transient Ischemic Attack According to Clinical Characteristics, Perception of the Event, and Predicted Risk of Stroke
Authors: Giles Matthew F. , Flossman Enrico , Rothwell Peter M.
Published: March 2006

Background and Purpose—

Little research has been done on patients’ behavior after transient ischemic attack (TIA). Recent data on the high early risk of stroke after TIA mean that emergency action after TIA is essential for effective secondary prevention. We therefore studied patients’ behavior immediately after TIA according to their perceptions, clinical characteristics, and predicted stroke risk.

Methods—

Consecutive patients with TIA participating in the Oxford Vascular Study or attending dedicated hospital clinics in Oxfordshire, UK, were interviewed. Predicted stroke risk was calculated using 2 validated scores.

Results—

Of 241 patients, 107 (44.4%) sought medical attention within hours of the event, although only 24 of these attended the emergency department. A total of 107 (44.4%) delayed seeking medical attention for ≥1 day. Correct recognition of symptoms (42.2% of patients) was not associated with less delay. However, patients with motor symptoms or duration of symptoms ≥1 hour were more likely to seek emergency attention (hazard ratio, 2.1; 95% CI, 1.4 to 3.2;
P
=0.00005), as were those at higher predicted stroke risk (
P
=0.001). The other main correlate with delay was the day of the week on which the TIA occurred (
P
<0.001), with greater delays at the weekend. Delay was unrelated to age, sex, or other vascular risk factors.

Conclusions—

Many patients delay seeking medical attention after a TIA irrespective of correct recognition of symptoms, although patients at higher predicted risk of stroke do act more quickly. Public education about both the urgency and nature of TIA is required.