bluuebunny/crossref_metadata_2025 huggingface dataset:
The functional role of blood platelet components in angiogenesis
Authors: Silvia Uwe , Fischer Silvia , Morgenstern Eberhard , Hammes Hans-Peter , Rhee Joong-Sup , Black Martin , Preissner Klaus
Published: July 2004

The process of neovascularization greatly depends on the induction of the angiogenic phenotype of endothelial cells that is strictly controlled by humoral factors as well as by cellular communications in the vascular system. Although blood platelets contain several secretable pro-and antiangiogenic components, their overall role in angiogenesis remains poorly understood. In a mouse model of hypoxia-induced retinal angiogenesis, the situation of thrombocytopenia as well as inhibition of platelet aggregation by a highly specific αIIbß3-integrin antagonist or acetyl salicylic acid (Aspirin™) administration, respectively, resulted in about 35-50% reduction of retinal neovascularization, compatible with a significant contribution of blood platelets in angiogenesis. Platelet remnants and microvesicles were found at sites of angiogenic sprouts. In vitro isolated platelets incorporated in a fibrin gel induced capillary sprouting of microvascular endothelial cells. Similarly, platelet releasate elevated the permeability of confluent endothelial cell monolayers to the same extent as hypoxia did. Platelet-derivedVEGF as well as butanol-extractable lipid mediators were identified as predominant activators of angiogenesis, particularly of microvascular endothelial cell proliferation and migration. In addition, a synergistic effect between platelet-derived VEGF and bFGF in capillary sprouting and endothelial cell proliferation was found. Based on this proangiogenic role of platelets in neovascularization, anti-platelet substances can be considered as potent inhibitors of angiogenesis.
Antithrombin reduces ischemia/reperfusion-induced liver injury in rats by activation of cyclooxygenase-1
Authors: Harada Naoaki , Uchiba Mitsuhiro , Kushimoto Shigeki , Isobe Hirotaka , Okajima Kenji
Published: July 2004

This study was conducted to determine which isoform of cyclooxygenase (COX) is more significantly involved in the antithrombin (AT)-induced increase in prostaglandin production in the liver of rats, subjected to hepatic ischemia/reperfusion (I/R). Hepatic tissue levels of 6-keto-PGF1α, a stable metabolite of prostacyclin (PGI2), and PGE2 were transiently increased 1 hour after reperfusion. Thereafter, hepatic PGE2 levels were gradually increased until 6 hours after reperfusion, while hepatic 6-keto-PGF1α levels were decreased to the pre-ischemia levels at 6 hours after reperfusion. AT significantly enhanced increases in hepatic tissue levels of 6-keto-PGF1α and PGE2 seen 1 hour after reperfusion, while it inhibited increases in hepatic PGE2 levels seen 6 h after reperfusion. Neither dansyl-Glu-Gly-Arg-chloromethyl ketone-treated factor Xa (DEGR-Xa), a selective inhibitor of thrombin generation, nor Trp49-modified AT which lacks affinity for heparin, showed any effects on these changes. Pretreatment with indomethacin (IM), a non-selective inhibitor of COX, inhibited AT-induced increases in hepatic tissue levels of 6-keto-PGF1α and PGE2 seen 1 hour after reperfusion, whereas pretreatment with NS-398, a selective inhibitor of COX-2, did not. The increase in hepatic tissue blood flow and inhibition of hepatic inflammatory responses seen in animals given AT were reversed by pretreatment with IM, but were not affected by pretreatment with NS-398. Administration of iloprost, a stable analog of PGI2, and PGE2 produced effects similar to those induced by AT. Increases in hepatic tissue levels of PGE2 6 hours after reperfusion were inhibited by pretreatment with NS-398. Although AT did not affect COX-1 mRNA levels 1 hour after reperfusion, it inhibited the I/R-induced increases in hepatic tissue levels of both PGE2 and COX-2 mRNA 6 hours after reperfusion. These observations strongly suggested that AT might reduce the I/R-induced liver injury by increasing the production of PGI2 and PGE2 through activation of COX-1. Furthermore, since TNF-a is capable of inducing COX-2, inhibition of TNF-a production by AT might inhibit COX-2-mediated PGE2 production. These effects induced by AT might contribute to its anti-inflammatory activity.
Compensated activation of coagulation in patients with abdominal aortic aneurysm: effects of heparin treatment prior to elective surgery
Authors: Szmidt Jacek , Bojakowski Krzystof , Grzela Tomasz , Palester-Chlebowczyk Magorzata , Jelenska Maria
Published: July 2004

Elective surgery of abdominal aortic aneurysm (AAA) sometimes leads to excessive bleeding and disseminated intravascular coagulation (DIC), even in patients with normal preoperative coagulation parameters. Coagulation screen, performed routinely before surgery is of limited value in the assessment of compensated activation of the haemostatic system. In this study, we used a number of additional tests (D-dimer, prothrombin fragment 1+2, antithrombin, and activation of fibrinolysis in the platelet poor plasma) for the diagnosis of compensated activation of the haemostatic system in AAA-patients. Ddimer and marker of thrombin generation (prothrombin fragment 1+2) positively correlated with each other (r = 0.768, P < 0.001). Out of 71 AAA patients, 15 patients had normal global coagulation times, but those with a Ddimer concentration above 3000 ng/ml were selected for preoperative low molecular weight heparin (LMWH) treatment. Administration of LMWH diminished coagulation abnormalities (D-dimer and prothrombin fragment 1+2 decreased significantly) and resulted in the increase of platelet number and fibrinogen concentration, indicating their previous consumption. Despite differences in aneurysm diameters between the groups of 15 LMWH treated patients (mean 70.9 ± 16 mm) and the reference group of 20 untreated AAA patients (mean 52.3 ± 8.0 mm), intraoperative parameters (operation time, blood loss and transfusion demands) were similar.
Dissecting the roles of endothelin,TGF-β and GM-CSF on myofibroblast differentiation by keratinocytes
Authors: Shephard Pierre , Hinz Boris , Smola-Hess Sigrun , Meister Jean-Jacques , Krieg Thomas , Smola Hans
Published: July 2004

Myofibroblasts are specialized fibroblasts that contribute to wound healing by producing extracellular matrix and by contracting the granulation tissue.They appear in a phase of wound healing when the dermis strongly interacts with activated epidermal keratinocytes. Direct co-culture with keratinocytes upregulates TGF-β???????????activity and also induces fibroblast to differentiate into α-smooth muscle actin (αSMA)-positive myofibroblasts. TGF-βactivity alone cannot completely account for αSMA induction in these co-cultures, and here we analyze mechanical force generation, another potent inducer of myofibroblast differentiation in this model. Using deformable silicone substrates, we show that contractile activity of fibroblasts is already induced after 1-2-days of co-culture, when fibroblasts are generally αSMA negative. Endothelin-1 (ET-1), the most potent inducer of smooth muscle cell contraction, was up-regulated in co-cultures, while blocking ET-1 with the ET receptor inhibitor PD156252 inhibited contraction in these early co-cultures. In 4-5 days of co-culture, however, fibroblast contractile activity correlated with an increased expression of αSMA expression. Stimulation of fibroblast mono-cultures with ET-1 in a low serum medium did not induce αSMA expression; however, ET-1 did synergize with TGF-β. Surprisingly, GM-CSF, another mediatorstimulating myofibroblast differentiation in granulation tissue, inhibited αSMA expression in fibroblasts, costimulated with TGF-β and ET-1. GM-CSF activated NFκB, thus interfering with TGF-β signaling. Blocking TGF-β and ET-1 largely impaired αSMA induction in co-cultures at day 7 and, in combination, almost completely prevented αSMA induction. Our results dissect the roles of TGF-β and ET-1 on mechanical force generation in keratinocyte-fibroblast co-cultures, and identify GM-CSF as an inducer of myofibroblasts acting indirectly.
Incidence of post-thrombotic syndrome and its association with various risk factors in a cohort of Spanish patients after one year of follow-up following acute deep venous thrombosis
Authors: Labiós Manuel , Portolés Olga , Guillén Marisa , Corella Dolores , Francés Francesc , Martínez Marcial , Gil Joaquin , Saiz Carmen , Gabriel Francisco
Published: July 2004

Post-thrombotic syndrome (PTS) is a frequent complication of deep venous thrombosis (DVT). However, neither the incidence nor the moment of PTS appearance are known. The main reason are the criteria used to define PTS, the characteristics of the patients, the study design and the time of follow-up. Our aims were to estimate the early incidence of PTS and its associated factors in a cohort of carefully defined DVT patients. 135 patients with a previous episode of acute idiopathic, phlebographically confirmed DVT, in the lower limbs, were followed up over 12 months. Phlebography was then repeated to determine the appearance of PTS. In addition, we used a validated clinical scale in order to assess the correlation between the clinical and phlebographical diagnosis of the PTS. This scale was applied at 6 and 12 months. The incidence of phlebographically confirmed PTS within the first year was 56.3% for the isolated PTS and 5.9% for PTS plus recurrent DVT, regardless of age, sex, platelet count, INR, or anticoagulation. None of these patients could be diagnosed as having PTS using the clinical validated scale. However, those patients with phlebographically diagnosed PTS had a higher clinical score than those without (P = 0.012). The only factor related to a higher risk of developing a PTS was the localization of the DVT, subjects with both proximal and distal DVT having the highest incidence (P = 0.001). In conclusion, although patients had appropriate anticoagulation, early incidence of PTS was very high, thus making it necessary to develop better diagnostic methods in order to evaluate the PTS impact.
ADP induced platelet degranulation in healthy individuals is reduced by clopidogrel after pretreatment with atorvastatin
Authors: Piorkowski Michael , Weikert Ulf , Schwimmbeck Peter-Lothar , Martus Peter , Schultheiss Heinz-Peter , Rauch Ursula
Published: July 2004

Statins inhibit platelet reactivity and reduce blood thrombogenicity.The effectiveness of clopidogrel in inhibiting platelet reactivity was suggested to be reduced in the presence of atorvastatin due to shared enzymes in metabolism. Healthy individuals, 17 pretreated with atorvastatin (20 mg/d for 3 days) and 17 without pretreatment, as well as 15 patients with stable coronary artery disease (CAD) and concurrent atorvastatin therapy were started on clopidogrel (loading dose 300 mg, then 75 mg/d). P-selectin on platelet surface after stimulation with ADP or Thrombin Receptor Activating Peptide (TRAP) was flow cytometrically measured before and during clopidogrel administration. Whole blood platelet agglutination was tested by a platelet function assay.TRAP and - in trend - ADP induced p-selectin exposure was reduced by the atorvastatin pretreatment before clopidogrel was added. Combining clopidogrel with atorvastatin in the healthy individuals led to a further reduction in ADP-induced platelet p-selectin exposure. Clopidogrel also reduced platelet reactivity in CAD patients with concurrent atorvastatin medication. We conclude that pretreatment with atorvastatin reduces platelet reactivity before administration of clopidgrel. No drug interaction was seen, however, platelet inhibitory effects were observed during the treatment with clopidogrel and atorvastatin.
Platelet glycoprotein Ibα polymorphisms modulate the risk for myocardial infarction
Authors: Ozelo Margareth , Origa Andrea , Aranha Francisco , Mansur Antonio , Annichino-Bizzacchi Joyce , Costa Fernando , Pollak Eleanor , Arruda Valder
Published: July 2004

Platelet glycoprotein Iba (GPIba) gene polymorphisms have been reported to affect the risk of developing coronary heart disease. Here, within the GPIba gene, we determine the association between the variable number of tandem repeats (VNTR), the -5C/T Kozak sequence dimorphism, and the human platelet antigen (HPA)-2 polymorphisms with occurrence of myocardial infarction (MI). Patients (n=180) presenting survivors of MI were compared to 180 controls matched by age, gender, and race. Carriers of VNTR-CD genotype had a 2-fold higher risk for MI compared to controls. The prevalence of VNTR-BC was lower among patients than among controls (P=.007). These data are in agreement with recent reports of increased plug formation by human platelets containing VNTRCD but no other VNTR genotypes. Among patients, the number of vessels severely occluded was greater among carriers of the D-allele (P=.019) or VNTR-CD (P=.026) and lower among carriers of the C-allele (P=.003) or VNTR-CC (P=.0009) compared to non-carriers of these alleles. No influence was seen with the Kozak or HPA-2 polymorphisms. Determination of VNTR of the GPIba gene may prove useful for identifying high-risk individuals for MI.
Modulation of VEGF-induced endothelial cell cycle protein expression through cyclic AMP hydrolysis by PDE2 and PDE4
Authors: Favot Laure , Keravis Thérèse , Lugnier Claire
Published: July 2004

Endothelial cell proliferation in response to VEGF plays an important role in physiological and pathological angiogenesis. The role of PDE2 and PDE4 in VEGF-induced proliferation in HUVEC was investigated: 1) VEGF increased cAMP-hydrolytic activity by up-regulating the expression of PDE2 and PDE4 isozymes; 2) VEGF increased progression in cell cycle with an increase in p42/p44 MAP kinase, cyclin A and cyclin D1 expressions and with a decrease in p21waf1/cip1 and p27kip1 expressions; 3) EHNA (20 µM), a selective PDE2 inhibitor, RP73401 (10 µM), a selective PDE4 inhibitor blocked the VEGF-induced increase in p42/p44 MAP kinase expression; 4) RP73401, but not EHNA, blocked the VEGF-induced increase in cyclin A and decrease in p27kip1 expressions; 5) EHNA, contrary to RP73401, enhanced the VEGF-induced increase of cyclin A and decrease of p27kip1. EHNA and RP73401 together blocked the VEGF-induced increase in cyclin D1 and decrease in p21waf1/cip1 expressions; Inhibition of VEGF-upregulated PDE2 and PDE4 reversed the VEGF-induced alterations in cell cycle protein expression, bringing back endothelial cells to a non-proliferating status. Consequently, PDE2 and PDE4 inhibitions were able to inhibit VEGF-induced endothelial cell proliferation by restoring cell cycle key protein expression, and might thus be useful in excessive angiogenesis. Furthermore, the differences between PDE2 and PDE4 effects may suggest compartmentalized effects.
Regulated de novo biosynthesis of fibrinogen in extrahepatic epithelial cells in response to inflammation
Authors: Lawrence Sarah , Simpson-Haidaris Patricia
Published: July 2004

Hepatic fibrinogen (FBG) is upregulated during an acute phase response (APR) induced by glucocorticoids and interleukin (IL)-6. Furthermore, intestine and lung epithelium synthesize FBG after exposure to inflammatory mediators, and both plasma and lung cell-derived FBG, along with fibronectin, assemble in detergent-insoluble extracellular matrices (ECM) of pneumocytes and fibroblasts independent of thrombin or plasmin cleavage. An epitope cryptic in soluble FBG (β15-21) but exposed in matrix-FBG and fibrin induces cell proliferation and actin cytoskeleton reorganization during wound repair and angiogenesis. Although fibrin(ogen) is involved in hemostasis and homeostasis, mechanisms regulating extrahepatic FBG expression remain unexplored. Herein we examined FBG production by lung compared to liver epithelial cell lines in response to dexamethasone (DEX)+IL-6. Regulated synthesis of HepG2-FBG follows the pathway shown for constitutive synthesis by liver epithelium. Constitutive A549-FBG expression was not detectable, however, intracellular FBG precursors in DEX+IL-6-treated A549 lung cells were similar to HepG2 cells with two notable exceptions. The relative rate of chain synthesis in HepG2 cells was unequal, whereas nascent synthesis of all three chains occurred at equivalent rates in stimulated A549 cells. Unlike HepG2 cells, which rapidly secreted intact FBG, nascent dimeric FBG accumulated in the A549 cell-associated fraction prior to release into medium. Furthermore, soluble A549-FBG was susceptible to thrombin and plasmin cleavage. Interestingly, many functionally diverse proteins possess FBG-related domains that direct cell-fate determination during development or wound repair, suggesting that extrahepatic FBG biosynthesis evoked only during inflammation plays such a role during localized injury and repair to restore tissue homeostasis.
Do prothrombotic factors influence clinical phenotype of severe haemophilia? A review of the literature
Authors: van der Bom Johanna , Fischer Kathelijn , Grobbee Diederick , van den Berg H. , van Dijk Karin
Published: July 2004

There is considerable variability in bleeding patterns of severe haemophilia (<1% factor VIII). Knowledge of the contribution of thrombophilic factors in these patterns may improve individually tailored treatment strategies. We reviewed the literature regarding the relation between prothrombotic factors and clinical phenotype of severe haemophilia. Medline and EMBASE were searched for relevant articles. 9369 articles published between 1963 and September 2003 were screened and seven relevant papers were retrieved. Each of these reported on a different combination of thrombophilic factors. Presence of the factor V Leiden mutation appears to decrease the severity of severe haemophilia most consistently. Findings on other thrombophilic factors were inconclusive. There is a clear need for additional research on potential determinants of phenotypes of severe haemophilia before such knowledge can be translated into individual care for severe haemophilia patients with confidence.
Influence of polymorphisms in the factor VII gene promoter on activated factor VII levels and on the risk of myocardial infarction in advanced coronary atherosclerosis
Authors: Girelli Domenico , Bernardi Francesco , Ferraresi Paolo , Olivieri Oliviero , Pinotti Mirko , Martinelli Nicola , Manzato Franco , Friso Simonetta , Villa Giuliano , Pizzolo Francesca , Beltrame Federico , Corrocher Roberto , Bozzini Claudia
Published: July 2004

In this study, we investigate the influence of three factor VII (FVII) gene polymorphisms on activated FVII levels (FVIIa), and also on the risk of myocardial infarction (MI) in patients with advanced coronary atherosclerotic disease (CAD). The –323A2 allele in the promoter is known to be associated with low FVII levels, and has been suggested to protect against MI in some studies. The –402GA promoter polymorphism, that in vitro has been associated with having opposite effect, is less well studied clinically. For this study, plasma FVIIa levels and three FVII gene polymorphisms were assessed in 934 subjects of both sexes, all with an angiographic documentation of coronary vessels. Our results show that two promoter polymorphisms, plasma cholesterol, and gender, were significant predictors of FVIIa levels. The –402A allele was associated to a significant increase of FVIIa levels in males (by 19.2%). In a selected clinical model including the patients with severe CAD, with or without a thrombotic complication (MI), male carriers of the –402A had an increased risk of MI (OR=1.79; 95% CI 1.15-2.80). The –323A2 allele was associated to a significant decrease in FVIIa (by 36.02% in males, and 39.7% in females). Male carriers of the –323A2 were protected from MI (OR=0.6; 95% CI 0.39-0.94), but only after correction for the confounding effect of combined heterozygosity for the promoter polymorphisms. We can conclude that FVII gene polymorphisms with an opposite effect on FVIIa levels may modulate the risk of MI in males with advanced CAD. This study highlights a “within-gene” interaction, and the need to explore polymorphisms in candidate gene(s) in detail.
Prognosis of young ischemic stroke in Taiwan: impact of prothrombotic genetic polymorphisms
Authors: Yeh Poh-Shiow , Lin Huey-Juan , Lin Kao-Chang , Cheng Tain-Junn , Chang Chia-Yu , Ke Der-Shin , Li Yi-Heng
Published: July 2004

We investigated the effects of genetic factors on the prognosis of cerebral infarction in young adults in Taiwan. Because ischemic stroke with arterial occlusion or undetermined etiology is more likely to be related to a genetic prothrombotic state, 231 patients younger than 50 years (mean age 44.6 years, range 25 to 49 years) with acute ischemic stroke due to large artery atherosclerosis (n=90), small artery occlusion (n=114) or undetermined cause (n=27) were recruited and prospectively followed up for pre-determined outcome. On each patient, we screened the PlA1/PlA2 polymorphism of the platelet glycoprotein IIIa gene, 4G/5G polymorphism of the plasminogen activator inhibitor-1 gene, G10976A polymorphism of the factor VII gene, C677T polymorphism of the methylenetetrahydrofolate reductase gene, and 27 base-pair repeat polymorphism of the endothelial nitric oxide synthase gene. End points were the composite outcome events of stroke, myocardial infarction, and death from all causes. During a mean duration follow-up of 29 months, composite outcome events occurred in 33 patients. There was a higher annual incidence rate of composite outcome events during the first year (9.1%, 95% CI 5.9-13.9%) than in the subsequent 2 years (2.6%, 95% CI 1.2-5.6%, p=0.038). None of the genetic polymorphism was associated with the composite outcome events. Past history of coronary artery disease or cerebrovascular disease was the only independent predictor of the composite outcome events (HR 3.71, 95% CI 1.69-8.14, p=0.001) at the Cox regression analysis. Our data indicate that the prothrombotic genetic polymorphisms do not have a significant influence on the prognosis in young ischemic stroke due to arterial occlusion or undetermined causes in Taiwan.
Thrombotic complications in patients with hereditary bleeding disorders
Authors: Franchini Massimo
Published: July 2004

Thromboses in patients with hereditary bleeding disorders are uncommon. However, in some cases, the co-existence of prothrombotic risk factors may increase the likelihood of developing thrombotic complications in such patients. This review summarizes the cases of thrombosis reported in the literature and analyzes the most important risk factors for thrombosis in patients with a congenital bleeding tendency. In particular we focus on central venous catheter (CVC)-associated thrombosis, on the thrombotic complications of coagulation factor concentrate therapy and on the presence of prothrom-botic gene mutations. Data were identified by searches of the published literature, including PubMed, references from reviews and abstracts from the most important meetings on this topic. In conclusion, there is increasing evidence that thrombotic complications in patients with hereditary bleeding disorders have a multifactorial pathogenesis, depending on exogenous (coagulation factor replacement therapy, CVC, HIV infection) and/or endogenous (prothrombotic gene mutations) risk factors.
Targeted deletion of murine coagulation factor XII gene-a model for contact phase activation in vivo
Authors: Pauer Hans-Ulrich , Renné Thomas , Hemmerlein Bernhard , Legler Tobias , Fritzlar Saskia , Adham Ibrahim , Müller-Esterl Werner , Emons Guenter , Sancken Ulrich , Engel Wolfgang , Burfeind Peter
Published: July 2004

To analyze the biological role of factor XII (FXII, Hageman Factor) in vivo, we generated mice deficient for FXII using a gene targeting approach on two distinct genetic backgrounds, i.e. mixed C57Bl/6J X 129X1/SvJ and inbred 129X1/SvJ. Homozygous FXII knockout (FXII-/-) mice showed no FXII plasma activity and had a markedly prolonged activated partial thromboplastin time (aPTT). In contrast, coagulation factors XI, VIII, IX, X,VII,V, II and fibrinogen did not differ between FXII-/- mice and their wild-type littermates. Heterozygous matings segregated according to the Mendelian inheritance indicating that FXII deficiency does not increase fetal loss. Furthermore, matings of FXII-/- males and FXII-/females resulted in normal litter sizes demonstrating that total FXII deficiency in FXII-/females does not affect pregnancy outcome. Also, gross and histological anatomy of FXII-/mice was indistinguishable from that of their wild-type littermates on both genetic backgrounds. Thus it appears that deficiency of murine FXII does not cause thrombophilia or impaired fibrinolysis in vivo. These results indicate that FXII deficiency does not affect hemostasis in vivo and we anticipate that the FXII-/mice will be helpful to elucidate the biological role(s) of FXII in health and disease.
Reduced Vascular NO Bioavailability in Diabetes Increases Platelet Activation In Vivo
Authors: Schäfer Andreas , Alp Nicholas J. , Cai Shije , Lygate Craig A. , Neubauer Stefan , Eigenthaler Martin , Bauersachs Johann , Channon Keith M.
Published: July 2004

Objective—

Platelet activation is a feature of cardiovascular disease that is also characterized by endothelial dysfunction. The direct relationship between impaired endothelium-derived NO bioavailability and platelet activation remains unclear. We investigated whether acute inhibition of NO production modulates platelet activation in mice and whether specific rescue of endothelial function in diabetes modifies platelet activation.

Methods and Results—

Intravenous injection of the NO synthase inhibitor
N
G
-nitro-
l
-arginine methyl ester in wild-type (WT) mice significantly reduced platelet vasodilator-stimulated phosphoprotein (VASP) phosphorylation and increased platelet surface expression of P-selectin, CD40 ligand, and fibrinogen platelet binding, demonstrating that NO production exerts tonic inhibition of platelet activation in mice. Diabetes was induced by streptozotocin injection in WT or endothelial-targeted guanosine 5′-triphosphate cyclohydrolase I (GCH)-transgenic (GCH-Tg) mice protected from endothelial dysfunction in diabetes by sustained levels of tetrahydrobiopterin in vascular endothelium. Platelet VASP phosphorylation was significantly reduced in diabetic WT but not in diabetic GCH-Tg mice. P-selectin, CD40 ligand expression, and fibrinogen binding were increased in diabetic WT mice but remained unchanged compared with controls in endothelial-targeted GCH-Tg mice.

Conclusion—

Platelet activation results from acute and chronic reduction in NO bioactivity. Rescue of platelet activation in diabetes by endothelial-specific restoration of NO production demonstrates that platelet function in vivo is principally regulated by endothelium-derived NO.
Potential Role for Mitogen-Activated Protein Kinase Phosphatase-1 in the Development of Atherosclerotic Lesions in Mouse Models
Authors: Reddy Srinivasa T. , Nguyen Julie T. , Grijalva Victor , Hough Greg , Hama Susan , Navab Mohamad , Fogelman Alan M.
Published: July 2004

Objective—

Mitogen-activated protein kinase phosphatase-1 (MKP-1) is one of several oxidized-
l
-α-1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphorylcholine (Ox-PAPC)-induced genes identified in human aortic endothelial cells (HAEC). We previously reported that MKP-1 activity is required for Ox-PAPC–mediated endothelial/monocyte interactions; however, an in vivo role of MKP-1 in atherogenesis has not been investigated.

Methods and Results—

We now report that MKP-1 protein is expressed in the atherosclerotic lesions of mice. MKP-1 mRNA expression is highly induced in C57BL6/J mice on an atherogenic diet, low-density lipoprotein receptor (LDLR) (−/−) mice on a Western diet, and 10-week or older ApoE (−/−) mice on a chow diet. In ApoE (−/−) mice treated with 1 mg/mL of sodium orthovanadate (NaOV), a specific inhibitor of tyrosine phosphatases including MKP-1, total phosphatase activity and MKP-1 protein were decreased in both the aortic lesions and liver lysates. In 3 animal models of atherosclerosis [C57BL6/J mice on an atherogenic diet for 15 weeks, LDLR (−/−) mice on a Western diet for 10 weeks, and ApoE (−/−) mice on a chow diet for 8 weeks], mice treated with NaOV had significantly smaller atherosclerotic lesions when compared with the control group.

Conclusion—

MKP-1 expression is associated with hypercholesterolemia and atherosclerosis, and inhibition of MKP-1 activity may prevent atherosclerotic lesion development in mice.
Homeobox Protein Hex Facilitates Serum Responsive Factor–Mediated Activation of the SM22α Gene Transcription in Embryonic Fibroblasts
Authors: Oyama Yuko , Kawai-Kowase Keiko , Sekiguchi Kenichi , Sato Mahito , Sato Hiroko , Yamazaki Miki , Ohyama Yoshio , Aihara Yasushi , Iso Tatsuya , Okamaoto Eichi , Nagai Ryozo , Kurabayashi Masahiko
Published: July 2004

Objective—

Hex (hematopoietically expressed homeobox), a member of homeobox family of transcription factors, has been implicated in the vascular development because of its expression in hemangioblast, a hypothetical stem cell that gives rise to both angioblasts and hematopoietic lineages. In the present study, we examined the role of Hex in the differentiation of vascular smooth muscle cells.

Methods and Results—

We constructed adenovirus expressing Hex, to which we refer to as AxCA/Hex, and transduced murine embryonic fibroblasts, 10T1/2 cells. Northern blot analyses showed that Hex increased the mRNA levels of smooth muscle α-actin and SM22α but not of calponin and smooth muscle myosin heavy chain. Transient transfection assays showed that Hex activates the transcription from the SM22α promoter in a CArG box-dependent manner. Electrophoretic mobility shift assays demonstrate that Hex is not able to bind to CArG box, but binding of serum responsive factor (SRF) to CArG box is enhanced in AxCA/Hex-transduced cells. Recombinant Hex protein produced by in vitro translation system augmented the binding activity of SRF to CArG box. Immunoprecipitation experiments revealed the physical association between Hex and SRF.

Conclusions—

Hex induces transcription of the SM22α gene by facilitating the interaction between SRF and its cognate binding site in pluripotent embryonic fibroblasts.
Regulation of Vascular L-type Ca
2+
Channels by Phosphatidylinositol 3,4,5-Trisphosphate
Authors: Le Blanc Catherine , Mironneau Chantal , Barbot Caroline , Henaff Morgana , Bondeva Tzvetanka , Wetzker Reinhard , Macrez Nathalie
Published: July 2004

Modulation of voltage-gated L-type Ca
2+
channels by phosphoinositide 3-kinase (PI3K) regulates Ca
2+
entry and plays a crucial role in vascular excitation-contraction coupling. Angiotensin II (Ang II) activates Ca
2+
entry by stimulating L-type Ca
2+
channels through Gβγ-sensitive PI3Kγ in portal vein myocytes. Moreover, PI3K and Ca
2+
entry activation have been reported to be necessary for receptor tyrosine kinase-coupled and G protein-coupled receptor-induced DNA synthesis in vascular cells. We have previously shown that tyrosine kinase-regulated class Ia and G protein-regulated class Ib PI3Ks are able to modulate vascular L-type Ca
2+
channels. PI3Ks display 2 enzymatic activities: a lipid-kinase activity leading to the formation of phosphatidylinositol 3,4,5-trisphosphate [PI(3,4,5)P
3
or PIP3] and a serine-kinase activity. Here we show that exogenous PIP3 applied into the cell through the patch pipette is able to reproduce the Ca
2+
channel-stimulating effect of Ang II and PI3Ks. Moreover, the Ang II-induced PI3K-mediated stimulation of Ca
2+
channel and the resulting increase in cytosolic Ca
2+
concentration are blocked by the anti-PIP3 antibody. Mutants of PI3Kγ transfected into vascular myocytes also revealed the essential role of the lipid-kinase activity of PI3Kγ in Ang II-induced Ca
2+
responses. These results suggest that PIP3 is necessary and sufficient to activate a Ca
2+
influx in vascular myocytes stimulated by Ang II.
Glucose-Potentiated Chemotaxis in Human Vascular Smooth Muscle Is Dependent on Cross-Talk Between the PI3K and MAPK Signaling Pathways
Authors: Campbell Malcolm , Allen William E. , Sawyer Carol , Vanhaesebroeck Bart , Trimble Elisabeth R.
Published: July 2004

Atheroma formation involves the movement of vascular smooth muscle cells (VSMC) into the subendothelial space. The aim of this study was to determine the involvement of PI3K and MAPK pathways and the importance of cross-talk between these pathways, in glucose-potentiated VSMC chemotaxis to serum factors. VSMC chemotaxis occurred in a serum gradient in 25 mmol/L glucose (but not in 5 mmol/L glucose) in association with increased phosphorylation (activation) of Akt and ERK1/2 in PI3K and MAPK pathways, respectively. Inhibitors of these pathways blocked chemotaxis, as did an mTOR inhibitor. VSMC expressed all class IA PI3K isoforms, but microinjection experiments demonstrated that only the p110β isoform was involved in chemotaxis. ERK1/2 phosphorylation was reduced not only by MAPK pathway inhibitors but also by PI3K and mTOR inhibitors; when PI3K was inhibited, ERK phosphorylation could be induced by microinjected activated Akt, indicating important cross-talk between the PI3K and ERK1/2 pathways. Glucose-potentiated phosphorylation of molecules in the p38 and JNK MAPK pathways inhibited these pathways but did not affect chemotaxis. The statin, mevinolin, blocked chemotaxis through its effects on the MAPK pathway. Mevinolin-inhibited chemotaxis was restored by farnesylpyrophosphate but not by geranylgeranylpyrophosphate; in the absence of mevinolin, inhibition of farnesyltransferase reduced ERK phosphorylation and blocked chemotaxis, indicating a role for the Ras family of GTPases (MAPK pathway) under these conditions. In conclusion, glucose sensitizes VSMC to serum, inducing chemotaxis via pathways involving p110β-PI3K, Akt, mTOR, and ERK1/2 MAPK. Cross-talk between the PI3K and MAPK pathways is necessary for VSMC chemotaxis under these conditions.
Transcriptional Regulation of Cardiac Progenitor Cell Populations
Authors: Masino Amanda M. , Gallardo Teresa D. , Wilcox Celeste A. , Olson Eric N. , Williams R. Sanders , Garry Daniel J.
Published: July 2004

Transcriptome-wide analysis of dynamically regulated progenitor cell populations has the potential to elucidate key aspects of cardiac development. The heart, as the first organ to develop in the mammal, is a technically challenging but clinically relevant target for study. To define the transcriptional program of the cardiac progenitor, we used a novel transgenic strategy and fluorescence-activated cell sorting to reliably label and isolate cardiac progenitors directly from mouse embryos. Pure populations of cardiac progenitor cells were isolated from the cardiac crescent and 2 subsequent stages of heart development: the linear heart tube and the looping heart. RNA was isolated from stage-specific cardiac progenitors and subjected to transcriptome analysis by oligonucleotide array hybridization. The cardiac transcriptional regulatory programs were compared with the molecular programs of age-matched noncardiac embryonic cells, embryonic stem cells, adult cardiomyocytes, and each other to identify sets of genes exhibiting differential expression in the cardiac progenitor cell population. These results define the transcriptional profile of mammalian cardiac progenitor cells and provide insight into the molecular regulation of the earliest periods of heart development.
Targeting Neuroprotection Clinical Trials to Ischemic Stroke Patients With Potential to Benefit From Therapy
Authors: Weir Christopher J. , Kaste Markku , Lees Kennedy R.
Published: July 2004

Background and Purpose—

Clinical trials of neuroprotective drugs have had limited success. We investigated whether selecting patients according to prognostic features would improve the statistical power of a trial to identify an efficacious treatment.

Methods—

Using placebo data from the Glycine Antagonist in Neuroprotection (GAIN) International and National Institute of Neurological Disorders and Stroke (NINDS) recombinant tissue plasminogen activator (rtPA) clinical trials, we developed and validated simple prognostic models for stroke trial end points: Barthel Index ≥95, modified Rankin Scale ≤1, National Institutes of Health Stroke Scale ≤1, and Glasgow Outcome Scale=1. Using these models, we simulated 1000 clinical trials and estimated, under several hypothetical treatment effect patterns of neuroprotection, the effect on statistical power of including only patients with moderate prognosis. We calculated the number of patients that would have to be enrolled to maintain the statistical power achieved in selecting the whole trial population. Reanalysis of actual data from the NINDS rtPA trials confirmed the results independently.

Results—

Selecting patients with moderate prognosis (predicted probability of favorable outcome 0.2 to 0.8) enabled a sample size reduction, without loss of statistical power, of between 54.6% (51.3% to 57.6%) and 68.6% (66.0% to 71.1%), depending on the treatment effect pattern and outcome measure. These benefits were largely due to the exclusion of patients with poor prognosis.

Conclusions—

Targeting patients with potential to benefit enables a substantial sample size reduction without compromising statistical power or duration of recruitment. As part of a broader trial design strategy, informed use of prognostic data available acutely would help in identifying effective neuroprotective treatments.
Increased Stiffness of the Carotid Wall Material in Patients With Spontaneous Cervical Artery Dissection
Authors: Calvet David , Boutouyrie Pierre , Touze Emmanuel , Laloux Brigitte , Mas Jean-Louis , Laurent Stéphane
Published: July 2004

Background and Purpose—

The cause of spontaneous cervical artery dissection (sCAD) is largely unknown. An underlying connective tissue disorder has often been postulated, but arterial mechanical properties have rarely been studied. The study aim was to determine the elastic properties of a cervical artery, the common carotid artery, and a distal muscular artery, the radial artery in sCAD patients.

Methods—

We studied 32 patients with previous sCAD (median delay: 2.2 years) and 32 control subjects with similar age and blood pressure. Internal diameter, intima-media thickness, distensibility, and Young’s elastic modulus were determined at the site of the right and left common carotid arteries and the radial artery using noninvasive high-resolution echotracking systems.

Results—

In patients with previous sCAD, cross-sectional distensibility and compliance of the affected carotid artery did not differ from those of the contralateral carotid artery. Young’s elastic modulus (ie, the stiffness of the wall material) was 58% higher (0.44±0.32 versus 0.28±0.15 kPa·10
3
,
P
<0.001) and circumferential wall stress was 14% higher (56±12 versus 49±12 kPa,
P
<0.001) in sCAD patients than in controls. The highest tertile of common carotid artery Young’s elastic modulus was associated with an 8-fold higher risk of sCAD. Aortic stiffness, assessed from the carotid-femoral pulse wave velocity, and radial artery parameters did not differ between sCAD and controls.

Conclusions—

Carotid arteries, but not aorta and radial artery, displayed abnormal elastic properties in sCAD patients. Higher stiffness of carotid wall material and circumferential wall stress could increase the risk of dissection in these patients.
Measuring Carotid Stenosis on Contrast-Enhanced Magnetic Resonance Angiography
Authors: U-King-Im Jean Marie K.S. , Trivedi Rikin A. , Cross Justin J. , Higgins Nicholas J.P. , Hollingworth William , Graves Martin , Joubert Ilse , Kirkpatrick Peter J. , Antoun Nagui M. , Gillard Jonathan H.
Published: July 2004

Background and Purpose—

The aim of this study was to compare diagnostic performance and reproducibility of 3 different methods of quantifying stenosis on contrast-enhanced magnetic resonance angiography (CEMRA), with intra-arterial digital subtraction angiography (DSA) as the reference standard.

Methods—

167 symptomatic patients scheduled for DSA, after screening Doppler ultrasound, were prospectively recruited to undergo CEMRA. Severity of stenosis was measured according to the North American Symptomatic Trial Collaborators (NASCET), European Carotid Surgery Trial (ECST), and the common carotid (CC) methods. Measurements for each method were made for 284 vessels (142 included patients) on both CEMRA and DSA in a blinded and randomized manner by 3 independent attending neuroradiologists.

Results—

Significant differences in prevalence of severe stenosis were seen with the 3 methods on both DSA and CEMRA, with ECST yielding the least and NASCET the most cases of severe stenosis. Overall, all 3 methods performed similarly well in terms of intermodality correlation and agreement. No significant differences in interobserver agreement were found on either modality. With CEMRA, however, we found a significantly lower sensitivity for detection of severe stenosis with ECST (79.8%) compared with NASCET (93.0%), with DSA as reference standard.

Conclusions—

Uniformity of carotid stenosis measurement methods is desirable because patient management may otherwise differ substantially. All 3 methods are adequate for use with DSA. With CEMRA, however, this study supports use of the NASCET method because of improved sensitivity for detecting severe stenosis.
Online Adaptive Decision Trees
Authors: Basak Jayanta
Published: July 2004

Decision trees and neural networks are widely used tools for pattern classification. Decision trees provide highly localized representation, whereas neural networks provide a distributed but compact representation of the decision space. Decision trees cannot be induced in the online mode, and they are not adaptive to changing environment, whereas neural networks are inherently capable of online learning and adpativity. Here we provide a classification scheme called online adaptive decision trees (OADT), which is a tree-structured network like the decision trees and capable of online learning like neural networks. A new objective measure is derived for supervised learning with OADT. Experimental results validate the effectiveness of the proposed classification scheme. Also, with certain real-life data sets, we find that OADT performs better than two widely used models: the hierarchical mixture of experts and multilayer perceptron.
Recurrent Network with Large Representational Capacity
Authors: Domijan Drazen
Published: July 2004

A recurrent network is proposed with the ability to bind image features into a unified surface representation within a single layer and without capacity limitations or border effects. A group of cells belonging to the same object or surface is labeled with the same activity amplitude, while cells in different groups are kept segregated due to lateral inhibition. Labeling is achieved by activity spreading through local excitatory connections. In order to prevent uncontrolled spreading, a separate network computes the intensity difference between neighboring locations and signals the presence of the surface boundary, which constrains local excitation. The quality of surface representation is not compromised due to the self-excitation.

The model is also applied on gray-level images. In order to remove small, noisy regions, a feedforward network is proposed that computes the size of surfaces. Size estimation is based on the difference of dendritic inhibition in lateral excitatory and inhibitory pathways, which allows the network to selectively integrate signals only from cells with the same activity amplitude. When the output of the size estimation network is combined with the recurrent network, good segmentation results are obtained. Both networks are based on biophysically realistic mechanisms such as dendritic inhibition and multiplicative integration among different dendritic branches.
Failure of Motor Learning for Large Initial Errors
Authors: Sanger Terence D.
Published: July 2004

For certain complex motor tasks, humans may experience the frustration of a lack of improvement despite repeated practice. We investigate a computational basis for failure of motor learning when there is no prior information about the system to be controlled and when it is not practical to perform a thorough random exploration of the set of possible commands. In this case, if the desired movement has never yet been performed, then it may not be possible to learn the correct motor commands since there will be no appropriate training examples. We derive the mathematical basis for this phenomenon when the controller can be modeled as a linear combination of nonlinear basis functions trained using a gradient descent learning rule on the observed commands and their results. We show that there are two failure modes for which continued training examples will never lead to improvement in performance. We suggest that this may provide a model for the lack of improvement in human skills that can occur despite repeated practice of a complex task.
Optimal Reduced-Set Vectors for Support Vector Machines with a Quadratic Kernel
Authors: Thies Thorsten , Weber Frank
Published: July 2004

To reduce computational cost, the discriminant function of a support vector machine (SVM) should be represented using as few vectors as possible. This problem has been tackled in different ways. In this article, we develop an explicit solution in the case of a general quadratic kernel k(x, x′) = (C + Dx⊺x′)2. For a given number of vectors, this solution provides the best possible approximation and can even recover the discriminant function if the number of used vectors is large enough. The key idea is to express the inhomogeneous kernel as a homogeneous kernel on a space having one dimension more than the original one and to follow the approach of Burges (1996).
Stochastic Reasoning, Free Energy, and Information Geometry
Authors: Ikeda Shiro , Tanaka Toshiyuki , Amari Shun-ichi
Published: July 2004

Belief propagation (BP) is a universal method of stochastic reasoning. It gives exact inference for stochastic models with tree interactions and works surprisingly well even if the models have loopy interactions. Its performance has been analyzed separately in many fields, such as AI, statistical physics, information theory, and information geometry. This article gives a unified framework for understanding BP and related methods and summarizes the results obtained in many fields. In particular, BP and its variants, including tree reparameterization and concave-convex procedure, are reformulated with information-geometrical terms, and their relations to the free energy function are elucidated from an information-geometrical viewpoint. We then propose a family of new algorithms. The stabilities of the algorithms are analyzed, and methods to accelerate them are investigated.
Doing Knowledge Transfer: Engaging Management and Labor with Research on Employee Health and Safety
Authors: Kramer Desre M. , Cole Donald C. , Leithwood Kenneth
Published: July 2004

In workplace health interventions, engaging management and union decision makers is considered important for the success of the project, yet little research has described the process of making this happen. A case study of a knowledge-transfer process is presented to describe the practices and processes adopted by a knowledge broker who engaged workplace parties in discussions on research on physical and psychosocial factors important for employee health. The process included one-on-one interactions between the knowledge broker and individuals to explain the research, to build trust and credibility, and to explore the applicability of the research to their work (sense making). It also included facilitated group sessions, where the groups explored how the research could solve problems within the workplace (social construction of knowledge). The workplace context offered multiple opportunities that helped and hindered the flow of research. Nevertheless, this intense, sustained, knowledge-transfer intervention noted conceptual, structural, and political knowledge use.