2011
Laminar shear, but not orbital shear, has a synergistic effect with thrombin stimulation on tissue factor expression in human umbilical vein endothelial cells
Rochier A, Nixon A, Yamashita N, Abe R, Abe R, Madri JA, Sumpio BE. Laminar shear, but not orbital shear, has a synergistic effect with thrombin stimulation on tissue factor expression in human umbilical vein endothelial cells. Journal Of Vascular Surgery 2011, 54: 480-488. PMID: 21367569, DOI: 10.1016/j.jvs.2011.01.002.Peer-Reviewed Original ResearchAnalysis of VarianceBlotting, WesternCell Culture TechniquesCells, CulturedEndothelial CellsEnzyme ActivationHumansMechanotransduction, CellularMitogen-Activated Protein Kinase 1Mitogen-Activated Protein Kinase 3P38 Mitogen-Activated Protein KinasesPhosphorylationProtein Kinase InhibitorsRNA, MessengerStress, MechanicalThrombinThromboplastinTime FactorsUp-RegulationPulsatile to-fro flow induces greater and sustained expression of tissue factor RNA in HUVEC than unidirectional laminar flow
Abe R, Yamashita N, Rochier A, Abe R, Nixon A, Madri JA, Sumpio BE. Pulsatile to-fro flow induces greater and sustained expression of tissue factor RNA in HUVEC than unidirectional laminar flow. AJP Heart And Circulatory Physiology 2011, 300: h1345-h1351. PMID: 21257914, PMCID: PMC3075035, DOI: 10.1152/ajpheart.01197.2010.Peer-Reviewed Original ResearchMeSH KeywordsAtherosclerosisCells, CulturedEndothelial CellsEnzyme InhibitorsFlavonoidsHumansImidazolesMAP Kinase Kinase KinasesP38 Mitogen-Activated Protein KinasesPulsatile FlowPyridinesStress, MechanicalThrombinThromboplastin
2010
Thrombospondin 1, Fibronectin, and Vitronectin are Differentially Dependent Upon RAS, ERK1/2, and p38 for Induction of Vascular Smooth Muscle Cell Chemotaxis
Willis AI, Sadowitz B, Fuse S, Maier KG, Lee TS, Wang XJ, Tuszynski GP, Sumpio BE, Gahtan V. Thrombospondin 1, Fibronectin, and Vitronectin are Differentially Dependent Upon RAS, ERK1/2, and p38 for Induction of Vascular Smooth Muscle Cell Chemotaxis. Vascular And Endovascular Surgery 2010, 45: 55-62. PMID: 21193465, DOI: 10.1177/1538574410387677.Peer-Reviewed Original ResearchMeSH KeywordsAnalysis of VarianceAnimalsCattleCells, CulturedChemotaxisFibronectinsHumansMitogen-Activated Protein Kinase 1Mitogen-Activated Protein Kinase 3Muscle, Smooth, VascularMyocytes, Smooth MuscleP38 Mitogen-Activated Protein KinasesProtein Kinase InhibitorsRas ProteinsThrombospondin 1TransfectionVitronectinConceptsVascular smooth muscle cellsThrombospondin-1Smooth muscle cell chemotaxisFarnesyl protein transferase inhibitorSignal transduction pathwaysProtein transferase inhibitorsVascular smooth muscle cell chemotaxisBovine vascular smooth muscle cellsTSP-1Ras N17Transduction pathwaysSecond messenger systemsP38Smooth muscle cellsERK1/2VSMC migrationTransferase inhibitorsPD098059Cell chemotaxisSB202190Muscle cellsMessenger systemsVitronectinRAChemotaxis
2008
The Effect of Different Frequencies of Stretch on Human Dermal Keratinocyte Proliferation and Survival
Nishimura K, Blume P, Ohgi S, Sumpio BE. The Effect of Different Frequencies of Stretch on Human Dermal Keratinocyte Proliferation and Survival. Journal Of Surgical Research 2008, 155: 125-131. PMID: 19059608, DOI: 10.1016/j.jss.2008.07.029.Peer-Reviewed Original ResearchConceptsERK 1/2P38 MAPKProtein kinaseKeratinocyte proliferation rateCell deathAkt inhibitorCyclic stretchDNA synthesisAktTransferase-mediated dUTP nick-end labeling stainingRepetitive stretchApoptosisMAPKDUTP nick end labeling stainingProliferation rateHuman dermalCell numberNick end labeling stainingTUNEL-positive cellsDermal keratinocytesStretchTerminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) stainingBrdU stainingKeratinocyte proliferationProliferation
2007
Role of Ligand-Specific Integrins in Endothelial Cell Alignment and Elongation Induced by Cyclic Strain
Hirayama Y, Sumpio BE. Role of Ligand-Specific Integrins in Endothelial Cell Alignment and Elongation Induced by Cyclic Strain. Endothelium 2007, 14: 275-283. PMID: 18080865, DOI: 10.1080/10623320701746248.Peer-Reviewed Original ResearchConceptsEndothelial cellsP38 MAPKAnti-alpha2 integrin antibodyMorphological changesP38 mitogen-activated protein kinase (MAPK) pathwayCycles/minIntegrin-blocking antibodiesP38 MAPK pathwayMitogen-activated protein kinase pathwayAlpha 5Integrin antibodyProtein kinase pathwayMAPK pathwayAntibodiesKinase pathwayMAPKMultiple biological processesActivationIntegrinsCritical roleCyclic strainPathway
2006
Nicotine enhances human vascular endothelial cell expression of ICAM-1 and VCAM-1 via protein kinase C, p38 mitogen-activated protein kinase, NF-κB, and AP-1
Ueno H, Pradhan S, Schlessel D, Hirasawa H, Sumpio BE. Nicotine enhances human vascular endothelial cell expression of ICAM-1 and VCAM-1 via protein kinase C, p38 mitogen-activated protein kinase, NF-κB, and AP-1. Cardiovascular Toxicology 2006, 6: 39-50. PMID: 16845181, DOI: 10.1385/ct:6:1:39.Peer-Reviewed Original ResearchConceptsHuman umbilical vein endothelial cellsICAM-1VCAM-1NF-κBAdhesion moleculesP38 mitogen-activated protein kinaseProtein kinase CMitogen-activated protein kinaseVascular cell adhesion moleculeEndothelial cellsExposure of HUVECsCellular adhesion molecule expressionAP-1Vascular endothelial cell expressionMajor risk factorEffects of nicotineEtiology of atherosclerosisP38 MAPKAdhesion molecule expressionIntercellular adhesion moleculeTranscription factor NF-κBCellular adhesion moleculesEndothelial cell expressionFactor NF-κBUmbilical vein endothelial cellsp38 Mitogen-Activated Protein Kinase Activation in Endothelial Cell Is Implicated in Cell Alignment and Elongation Induced by Fluid Shear Stress
Kadohama T, Akasaka N, Nishimura K, Hoshino Y, Sasajima T, Sumpio BE. p38 Mitogen-Activated Protein Kinase Activation in Endothelial Cell Is Implicated in Cell Alignment and Elongation Induced by Fluid Shear Stress. Endothelium 2006, 13: 43-50. PMID: 16885066, DOI: 10.1080/10623320600660219.Peer-Reviewed Original ResearchMeSH KeywordsAnimalsAntibodiesAtherosclerosisBlood PressureBlood VesselsCattleCell PolarityCell ShapeCells, CulturedDose-Response Relationship, DrugEndothelial CellsEnzyme ActivationEnzyme InhibitorsHemodynamicsMAP Kinase Signaling SystemP38 Mitogen-Activated Protein KinasesPhosphorylationRegional Blood FlowStress, MechanicalTime FactorsConceptsStatic endothelial cellsFluid shear stressP38 MAPKP38 Mitogen-Activated Protein Kinase ActivationMitogen-Activated Protein Kinase ActivationEndothelial cellsProtein kinase activationP38 MAPK inhibitor SB-203580Inhibitor SB 203580Cell alignmentProtein kinaseBovine aortic endothelial cellsLaminar shear stressKinase activationSB 203580P38 mitogenCultured bovine aortic endothelial cellsEC elongationAortic endothelial cellsMAPKCellsElongationActivationMorphometric analysisKinase
2005
Homocysteine promotes p38-dependent chemotaxis in bovine aortic smooth muscle cells
Akasaka K, Akasaka N, Di Luozzo G, Sasajima T, Sumpio BE. Homocysteine promotes p38-dependent chemotaxis in bovine aortic smooth muscle cells. Journal Of Vascular Surgery 2005, 41: 517-522. PMID: 15838488, DOI: 10.1016/j.jvs.2004.12.043.Peer-Reviewed Original ResearchMeSH KeywordsAnimalsBlotting, WesternCattleChemotaxisEnzyme InhibitorsHomocysteineImidazolesMuscle, Smooth, VascularP38 Mitogen-Activated Protein KinasesPhosphorylationPyridinesConceptsEffect of homocysteineMigration of SMCsLevels of homocysteineProgressive intimal thickeningAortic smooth muscle cellsSmooth muscle cell migrationBovine aortic smooth muscle cellsPotential therapeutic implicationsSmooth muscle cellsP38 activationExposure of SMCMuscle cell migrationSMC chemotaxisRisk factorsSelective blockadeIntimal thickeningTherapeutic implicationsP38-dependent pathwaySMC proliferationBoyden chamberChemotactic potentialMuscle cellsHomocysteineFetal bovine serumP38 inhibitorNicotine induces mitogen-activated protein kinase dependent vascular smooth muscle cell migration
Di Luozzo G, Pradhan S, Dhadwal AK, Chen A, Ueno H, Sumpio BE. Nicotine induces mitogen-activated protein kinase dependent vascular smooth muscle cell migration. Atherosclerosis 2005, 178: 271-277. PMID: 15694934, DOI: 10.1016/j.atherosclerosis.2004.09.017.Peer-Reviewed Original ResearchMeSH KeywordsAnimalsArteriosclerosisBlotting, WesternCattleCell MovementChemotactic FactorsGanglionic StimulantsMuscle, Smooth, VascularNicotineP38 Mitogen-Activated Protein KinasesSmokingConceptsVascular smooth muscle cell migrationSmooth muscle cell migrationMuscle cell migrationInhibitors of p38VSMC migrationMitogen-activated protein kinaseEndothelial cellsDevelopment of atherosclerosisEffects of nicotineCell migrationWestern blotting methodInjury modelVascular endotheliumCigarette smokeBoyden chamber chemotaxis assaysAortic VSMCsChemotactic effectMAPKs p38NicotineChemoattractant moleculesChemotaxis assaysCellular mechanismsUltrastructural changesVSMCP44/42 activationMAPKs (ERK½, p38) and AKT Can Be Phosphorylated by Shear Stress Independently of Platelet Endothelial Cell Adhesion Molecule-1 (CD31) in Vascular Endothelial Cells*
Sumpio BE, Yun S, Cordova AC, Haga M, Zhang J, Koh Y, Madri JA. MAPKs (ERK½, p38) and AKT Can Be Phosphorylated by Shear Stress Independently of Platelet Endothelial Cell Adhesion Molecule-1 (CD31) in Vascular Endothelial Cells*. Journal Of Biological Chemistry 2005, 280: 11185-11191. PMID: 15668248, DOI: 10.1074/jbc.m414631200.Peer-Reviewed Original ResearchAnimalsCattleCell CommunicationEndothelial CellsEnzyme ActivationHumansMechanoreceptorsMiceMitogen-Activated Protein Kinase 1Mitogen-Activated Protein Kinase 3P38 Mitogen-Activated Protein KinasesPhosphorylationPlatelet Endothelial Cell Adhesion Molecule-1Protein Serine-Threonine KinasesProto-Oncogene ProteinsProto-Oncogene Proteins c-aktStress, MechanicalTyrosine
2003
Fibronectin blocks p38 and jnk activation by cyclic strain in Caco-2 cells
Zhang J, Li W, Sumpio BE, Basson MD. Fibronectin blocks p38 and jnk activation by cyclic strain in Caco-2 cells. Biochemical And Biophysical Research Communications 2003, 306: 746-749. PMID: 12810082, DOI: 10.1016/s0006-291x(03)01044-1.Peer-Reviewed Original ResearchMeSH KeywordsCaco-2 CellsCell Culture TechniquesCollagen Type ICollagen Type IVFibronectinsHumansJNK Mitogen-Activated Protein KinasesLamininMitogen-Activated Protein KinasesP38 Mitogen-Activated Protein KinasesPhosphorylationStress, MechanicalConceptsIntestinal epithelial responsesIntestinal epithelial proliferationCaco-2 intestinal epithelial cellsIntestinal epithelial cellsHuman Caco-2 intestinal epithelial cellsCaco-2 cellsPlasma fibronectinInfectious conditionsEpithelial responseFibronectin levelsEpithelial proliferationIntestinal epitheliumEpithelial cellsRepetitive forcesBasement membraneCollagen ICollagen IVIntracellular signalingP38JNK activationActivationCellsStrain activationTissueFibronectinThrombospondin‐1‐induced vascular smooth muscle cell chemotaxis: The role of the type 3 repeat and carboxyl terminal domains
Lee T, Nesselroth SM, Olson ET, Esemuede N, Lawler J, Sumpio BE, Gahtan V. Thrombospondin‐1‐induced vascular smooth muscle cell chemotaxis: The role of the type 3 repeat and carboxyl terminal domains. Journal Of Cellular Biochemistry 2003, 89: 500-506. PMID: 12761883, DOI: 10.1002/jcb.10524.Peer-Reviewed Original ResearchMeSH KeywordsAnimalsCattleCells, CulturedChemotaxisEnzyme ActivationMitogen-Activated Protein KinasesMuscle, Smooth, VascularP38 Mitogen-Activated Protein KinasesThrombospondin 1ConceptsVSMC chemotaxisThrombospondin-1Acute phase reactantsSmooth muscle cell chemotaxisVascular diseaseVascular smooth muscle cell chemotaxisPhase reactantsExtracellular signal-regulated kinases 1Microchemotaxis chamberSignal-regulated kinases 1Serum-free mediumCell chemotaxisMatricellular glycoproteinActivate ERKWestern immunoblottingVSMCsT-testP38 activationP38 pathwayERKFusion proteinT3ChemotaxisKinase 1P38 kinaseAntisense basic fibroblast growth factor alters the time course of mitogen-activated protein kinase in arterialized vein graft remodeling
Yamashita A, Hanna AK, Hirata S, Dardik A, Sumpio BE. Antisense basic fibroblast growth factor alters the time course of mitogen-activated protein kinase in arterialized vein graft remodeling. Journal Of Vascular Surgery 2003, 37: 866-873. PMID: 12663990, DOI: 10.1067/mva.2003.130.Peer-Reviewed Original ResearchMeSH KeywordsAnimalsBlood Vessel ProsthesisCell Physiological PhenomenaEndothelium, VascularFibroblast Growth FactorsHyperplasiaJNK Mitogen-Activated Protein KinasesMitogen-Activated Protein KinasesModels, AnimalP38 Mitogen-Activated Protein KinasesProteinsRabbitsRegenerationRNA, AntisenseTime FactorsTransfectionVeinsConceptsProtein kinaseBasic fibroblast growth factorMAPK activationFibroblast growth factorMitogen-activated protein kinase (MAPK) familyC-Jun N-terminal protein kinaseProtein kinase familyExtracellular signal-regulated kinase 1/2Antisense basic fibroblast growth factorMitogen-activated protein kinaseSignal-regulated kinase 1/2Messenger RNA sequencesP38 kinase activationGrowth factor altersMAPK-dependent mechanismFibroblast growth factor activityGrowth factorKinase familyKinase activationGrowth factor activityPhosphorylation of MAPKsKinase 1/2RNA sequencesWestern blot analysisBasic fibroblast growth factor activityInvolvement of S6 kinase and p38 mitogen activated protein kinase pathways in strain‐induced alignment and proliferation of bovine aortic smooth muscle cells
Li W, Chen Q, Mills I, Sumpio BE. Involvement of S6 kinase and p38 mitogen activated protein kinase pathways in strain‐induced alignment and proliferation of bovine aortic smooth muscle cells. Journal Of Cellular Physiology 2003, 195: 202-209. PMID: 12652647, DOI: 10.1002/jcp.10230.Peer-Reviewed Original ResearchMeSH KeywordsAnimalsAortaCattleCell DivisionCells, CulturedDNA-Binding ProteinsEnzyme InhibitorsImidazolesImmunosuppressive AgentsMAP Kinase Signaling SystemMitogen-Activated Protein KinasesMuscle, Smooth, VascularMyocytes, Smooth MuscleP38 Mitogen-Activated Protein KinasesPyridinesRegional Blood FlowRibosomal Protein S6 KinasesSirolimusStress, MechanicalTranscription FactorsConceptsAortic smooth muscle cellsBovine aortic smooth muscle cellsKinase pathwaySmooth muscle cell phenotypeSmooth muscle cellsStrain-induced proliferationBovine aortic SMCS6 kinaseMuscle cell phenotypeSpecific inhibitorProliferation of SMCsActivation of p38SMC proliferationAortic SMCsMuscle cellsSMC alignmentModulation of vascular smooth muscle cell alignment by cyclic strain is dependent on reactive oxygen species and P38 mitogen-activated protein kinase
Chen Q, Li W, Quan Z, Sumpio BE. Modulation of vascular smooth muscle cell alignment by cyclic strain is dependent on reactive oxygen species and P38 mitogen-activated protein kinase. Journal Of Vascular Surgery 2003, 37: 660-668. PMID: 12618707, DOI: 10.1067/mva.2003.95.Peer-Reviewed Original ResearchMeSH KeywordsAnimalsAortaCattleCells, CulturedEnzyme ActivationEnzyme InhibitorsImidazolesJNK Mitogen-Activated Protein KinasesMitogen-Activated Protein Kinase 1Mitogen-Activated Protein Kinase 3Mitogen-Activated Protein KinasesMultienzyme ComplexesMuscle, Smooth, VascularNADH, NADPH OxidoreductasesNADPH OxidasesOnium CompoundsOxidation-ReductionP38 Mitogen-Activated Protein KinasesPhosphorylationPyridinesReactive Oxygen SpeciesStress, MechanicalRole of PP2A in the regulation of p38 MAPK activation in bovine aortic endothelial cells exposed to cyclic strain
Lee T, Kim SJ, Sumpio BE. Role of PP2A in the regulation of p38 MAPK activation in bovine aortic endothelial cells exposed to cyclic strain. Journal Of Cellular Physiology 2003, 194: 349-355. PMID: 12548554, DOI: 10.1002/jcp.10211.Peer-Reviewed Original ResearchMeSH KeywordsAnimalsAortaCattleCells, CulturedEndothelium, VascularEnzyme ActivationMitogen-Activated Protein KinasesP38 Mitogen-Activated Protein KinasesPhosphoprotein PhosphatasesPhosphorylationStress, MechanicalConceptsP38 MAPK activationMAPK activationCatalytic subunitBovine aortic endothelial cellsPhospho-p38 MAPKOkadaic acidProtein phosphatase type 2AInhibitor of PP2AAortic endothelial cellsEndothelial cellsProtein kinaseRapid phosphorylationPP2AP38 mitogenRegulatory roleCell lysatesPhosphatase activityPP2AcMAPKPhosphorylationCyclic strainSubunitsType 2ACyclic strain resultsCells
2002
SPHINGOSINE-1-PHOSPHATE STIMULATES HUMAN CACO-2 INTESTINAL EPITHELIAL PROLIFERATION VIA p38 ACTIVATION AND ACTIVATES ERK BY AN INDEPENDENT MECHANISM
THAMILSELVAN V, LI W, SUMPIO BE, BASSON MD. SPHINGOSINE-1-PHOSPHATE STIMULATES HUMAN CACO-2 INTESTINAL EPITHELIAL PROLIFERATION VIA p38 ACTIVATION AND ACTIVATES ERK BY AN INDEPENDENT MECHANISM. In Vitro Cellular & Developmental Biology - Animal 2002, 38: 246-253. PMID: 12197778, DOI: 10.1290/1071-2690(2002)038<0246:spshci>2.0.co;2.Peer-Reviewed Original ResearchConceptsExtracellular signal-regulated kinases 1Mitogen-activated protein kinaseMAP kinase kinaseCaco-2 proliferationMAPK activationHuman intestinal epithelial proliferationP38 activationCell typesSignal-regulated kinases 1Role of ERKMitogenic effectCaco-2 intestinal epithelial cellsIntracellular second messengerMEK inhibitionP38 MAPK activationCancer cell invasionKinase kinaseHuman Caco-2 intestinal epithelial cellsProtein kinaseStimulation of proliferationCell motilityIntestinal epithelial cell proliferationInhibitor PD98059ERK2ERK activation
2001
Integrin and FAK-mediated MAPK activation is required for cyclic strain mitogenic effects in Caco-2 cells
Li W, Duzgun A, Sumpio B, Basson M. Integrin and FAK-mediated MAPK activation is required for cyclic strain mitogenic effects in Caco-2 cells. AJP Gastrointestinal And Liver Physiology 2001, 280: g75-g87. PMID: 11123200, DOI: 10.1152/ajpgi.2001.280.1.g75.Peer-Reviewed Original ResearchMeSH KeywordsCaco-2 CellsCell DivisionCell MovementCytoskeletal ProteinsEnzyme InhibitorsExtracellular MatrixFlavonoidsFocal Adhesion Kinase 1Focal Adhesion Protein-Tyrosine KinasesGene Expression Regulation, EnzymologicHumansImidazolesIntegrinsIntestinesMAP Kinase Signaling SystemMitogen-Activated Protein Kinase 1Mitogen-Activated Protein Kinase 3Mitogen-Activated Protein Kinase 8Mitogen-Activated Protein Kinase 9Mitogen-Activated Protein KinasesNaphthalenesP38 Mitogen-Activated Protein KinasesPaxillinPhosphoproteinsPhosphorylationProtein-Tyrosine KinasesPyridinesStress, MechanicalTransfectionConceptsFocal adhesion kinaseMAPK extracellular signal-regulated kinaseCaco-2 cellsMitogen-activated protein kinase activationVitro kinase assaysProtein kinase activationSignal-regulated kinaseMitogenic effectProtein kinase C inhibitionBeta1 integrin subunitsCaco-2 proliferationKinase assaysAdhesion kinaseFAK activationERK signalsJNK1 activationKinase activationTerminal kinaseMAPK activationUpstream signalsC-JunFAK inhibitionP38 inhibitionIntegrin subunitsKinaseRole of p38 MAP kinase in endothelial cell alignment induced by fluid shear stress
Azuma N, Akasaka N, Kito H, Ikeda M, Gahtan V, Sasajima T, Sumpio B. Role of p38 MAP kinase in endothelial cell alignment induced by fluid shear stress. AJP Heart And Circulatory Physiology 2001, 280: h189-h197. PMID: 11123233, DOI: 10.1152/ajpheart.2001.280.1.h189.Peer-Reviewed Original ResearchAnimalsCattleCells, CulturedEndothelium, VascularEnzyme InhibitorsImidazolesImmunoblottingImmunohistochemistryIntracellular Signaling Peptides and ProteinsMitogen-Activated Protein KinasesMutationNeoplasm ProteinsP38 Mitogen-Activated Protein KinasesPlasmidsProtein Serine-Threonine KinasesPyridinesStress, MechanicalTransfection
2000
Role of mitogen-activated protein kinases in pulmonary endothelial cells exposed to cyclic strain
Kito H, Chen E, Wang X, Ikeda M, Azuma N, Nakajima N, Gahtan V, Sumpio B. Role of mitogen-activated protein kinases in pulmonary endothelial cells exposed to cyclic strain. Journal Of Applied Physiology 2000, 89: 2391-2400. PMID: 11090594, DOI: 10.1152/jappl.2000.89.6.2391.Peer-Reviewed Original ResearchMeSH KeywordsAnimalsCattleCell MovementCells, CulturedEndothelium, VascularEnzyme ActivationEnzyme InhibitorsFlavonoidsImidazolesJNK Mitogen-Activated Protein KinasesMitogen-Activated Protein KinasesP38 Mitogen-Activated Protein KinasesPhosphorylationPromoter Regions, GeneticPulmonary ArteryPyridinesResponse ElementsStress, MechanicalTetradecanoylphorbol AcetateTranscription Factor AP-1ConceptsPD 98059Activator protein-1SB 203580Protein kinaseBovine pulmonary arterial endothelial cellsPulmonary arterial endothelial cellsArterial endothelial cellsMAPK kinase kinase-1Mitogen-activated protein kinase activationMitogen-activated protein kinaseExtracellular signal-regulated kinaseTerminal protein kinaseKinase kinase 1AP-1/Cell alignmentERK kinase inhibitorProtein kinase activationSignal-regulated kinaseEndothelial cellsTranscriptional activationInactive mutantActivated MAPKsKinase activationKinase 1Transient transfection