ABSTRACT
We have previously described a monomeric rvWf fragment, Leu504-Lys728 that contains one disulfide bond linking Cys509-Cys695. This fragment, VCL, has previously been shown to inhibit vWf-ristocetin, asialo-vWf, and botrocetin-induced vWf binding and aggregation of platelets. VCL inhibited 50% of vWf binding to heparin, but it did not inhibit vWf binding to type I collagen. At a high shear force (2600-1 sec), VCL inhibited platelet adhesion to the subendothelial surface of human umbilical arteries. The maximum inhibition of platelet adhesion was 83 +/- 4% at a VCL concentration of 7.6 mumol/L. Various monoclonal anti-Very Late Activation antigens (VLA) antibodies were added to the VCL and tested for their ability to enhance the inhibition of platelet adhesion at high shear forces. Of all of the VLA antibodies tested, only the anti-VLA-2 antibody (176D7) inhibited platelet aggregation in the absence of VCL and enhanced the inhibition of platelet adhesion in the presence of VCL. The VLA-2 antibody and VCL together inhibited 96 +/- 4% of platelet adhesion at high shear forces.
Subject(s)
Hemorheology , Integrin beta1/physiology , Integrins/physiology , Peptide Fragments/pharmacology , Platelet Adhesiveness , Platelet Membrane Glycoproteins/physiology , Receptors, Cell Surface/physiology , Adult , Antibodies, Monoclonal/immunology , Antibodies, Monoclonal/pharmacology , Collagen/metabolism , Heparin/metabolism , Humans , Immunoglobulin Fab Fragments/immunology , Immunoglobulin Fab Fragments/pharmacology , Immunoglobulin G/immunology , Immunoglobulin G/pharmacology , Integrins/immunology , Muscle, Smooth, Vascular/metabolism , Platelet Adhesiveness/drug effects , Protein Binding/drug effects , Receptors, Collagen , Recombinant Proteins/pharmacology , Umbilical Arteries , von Willebrand Factor/physiologyABSTRACT
Men have significantly more atherosclerotic disease than women. Platelet-mediated thrombosis plays a role in the initiation of myocardial infarction and stroke. Citrated whole blood from male and female donors was perfused through an annular system over everted human umbilical artery segments. Comparisons were made between platelet adherence and thrombus formation on subendothelium, platelet aggregation in citrated whole blood, hematologic variables, and the bleeding time. Platelet spreading and adherence were approximately 22% greater with male blood (P < 0.001), whereas thrombus formation on subendothelium and collagen- and arachidonic acid-induced platelet aggregation did not show sex-related differences. Platelet aggregation with adenosine diphosphate was greater in women, related to their lower hematocrit values. By contrast, in women hematocrit values showed a slight but significant positive correlation with platelet adherence on subendothelium. Fibrinogen was significantly correlated with collagen- and adenosine-diphosphate-induced platelet aggregation and with platelet adherence, spreading, and thrombus formation on subendothelium. The mean bleeding time was slightly longer in women than in men (P = 0.118). Platelet aggregation was not associated with the bleeding time except for collagen-induced platelet aggregation in males; the latter was significantly correlated with platelet adherence and spreading in both sexes, while arachidonic acid-induced platelet aggregation predicted platelet adherence and spreading in males. Male blood shows enhanced primary hemostatic activity; this may predispose men to atherosclerosis.
Subject(s)
Blood Platelets/physiology , Endothelium, Vascular/pathology , Platelet Adhesiveness , Adult , Bleeding Time , Female , Fibrinogen/metabolism , Hematocrit , Humans , Male , Middle Aged , Platelet Aggregation , Sex Factors , Thrombosis/blood , Thrombosis/pathology , Umbilical Arteries/pathologyABSTRACT
Although clinical trials using laser and thermal angioplasty devices have been underway, the effects of pulsed laser and thermal ablation of atherosclerotic plaque on surface thrombogenicity are poorly understood. This study examined the changes in platelet adherence and thrombus formation on freshly harvested atherosclerotic aorta segments from Watanabe-heritable hyperlipidemic rabbits after ablation by two pulsed laser sources (308-nm xenon chloride excimer and 2,940-nm erbium:yttrium-aluminum-garnet [YAG] lasers) and a prototype catalytic hot-tip catheter. Specimens were placed in a modified Baumgartner annular chamber and perfused with citrated whole human blood, followed by quantitative morphometric analysis to determine the percent surface coverage by adherent platelets and thrombi in the treated and contiguous control areas. Pulsed excimer laser ablation of plaque did not change platelet adherence or thrombus formation in the treated versus control zones. However, photothermal plaque ablation with a pulsed erbium:YAG laser resulted in a 67% reduction in platelet adherence, compared with levels in control areas (from 16.7 +/- 2.2% to 5.5 +/- 1.8%; p less than 0.005). Similarly, after plaque ablation using a catalytic thermal angioplasty device, there was a 74% reduction in platelet adherence (from 29.2 +/- 5.1% to 7.7 +/- 1.6%; p less than 0.005) and a virtual absence of platelet thrombi (from 8.6 +/- 2.3% to 0.03 +/- 0.03%; p less than 0.005). This reduced surface thrombogenicity after plaque ablation with either an erbium:YAG laser or a catalytic hot-tip catheter suggests that thermal modifications in the arterial surface ultrastructure or thermal denaturation of surface proteins, or both, may be responsible for reduced platelet adherence. These in vitro findings indicate that controlled thermal plaque ablation by catheter-based techniques may elicit endovascular responses that can reduce early thrombus formation during angioplasty procedures.
Subject(s)
Angioplasty, Laser , Aortic Diseases/therapy , Arteriosclerosis/therapy , Hot Temperature/therapeutic use , Platelet Adhesiveness/physiology , Thrombosis/physiopathology , Animals , Aortic Diseases/pathology , Aortic Diseases/surgery , Arteriosclerosis/pathology , Arteriosclerosis/surgery , Catalysis , Catheterization/methods , Endothelium, Vascular/physiopathology , In Vitro Techniques , Perfusion , RabbitsABSTRACT
Arg-Gly-Asp (RGD)- and fibrinogen gamma-chain carboxyterminal (GQQHHLGGAKQAGDV) peptides inhibit fibrinogen, fibronectin (Fn), vitronectin, and von Willebrand factor (vWF) binding to the platelet glycoprotein IIb-IIIa complex (GP IIb-IIIa). GP IIb-IIIa, vWF, and Fn are essential for normal platelet adherence to subendothelium. We added peptides to normal citrated whole blood before perfusion over human umbilical artery subendothelium and evaluated platelet adherence morphometrically at high (2,600 s-1) and low (800 s-1) wall shear rates. We also examined the effects of the peptides on platelet adhesion to collagen in a static system. At the high wall shear rate, RGDS and GQQHHLGGAKQAGDV caused dose-dependent reduction in the surface coverage with spread and adherent platelets. Amino acid transposition and conservative substitutions of RGD peptides and the AGDV peptide significantly inhibited platelet adherence at 2,600 s-1. By contrast, the modified RGD peptides and AGDV do not affect adhesive protein binding to platelets. None of the native or modified RGD- or fibrinogen gamma-chain peptides significantly inhibited either platelet adherence to subendothelium at 800 s-1 or platelet adhesion to collagen. Our findings demonstrate that peptides that interfere with adhesive protein binding to GP IIb-IIIa inhibit platelet adherence to vascular subendothelium with flowing blood only at high wall shear rates. Platelet adherence to subendothelium at high wall shear rates appears to be mediated by different recognition specificities from those required for fluid-phase adhesive protein binding or static platelet adhesion.
Subject(s)
Endothelium, Vascular/metabolism , Fibrinogen/pharmacology , Oligopeptides/pharmacology , Platelet Adhesiveness/drug effects , Amino Acid Sequence , Collagen/metabolism , Endothelium, Vascular/physiology , Humans , Kinetics , Molecular Sequence Data , Protein Binding , Structure-Activity Relationship , Thrombin/pharmacology , Umbilical Arteries , von Willebrand Factor/metabolismABSTRACT
Platelet adherence and aggregation are important in the development of ischemic sequelae in atherosclerosis. To directly examine platelet interaction with plaque, everted, deendothelialized aortic fibrous plaques from Watanabe-heritable hyperlipidemic rabbits were exposed to flowing human blood in an annular perfusion chamber. Morphometry was used to compare platelet adherence and thrombi on this surface with that observed when blood was perfused over normal New Zealand White (NZW) rabbit aortic subendothelium. Platelet spreading, adherence, and thrombi on the atherosclerotic surface were approximately half that observed on NZW aorta. When surface proteins of NZW aorta were denatured by a hot-tip catheter, these parameters were reduced by 89-96%. The reduced thrombogenicity of uncomplicated plaques may help keep these narrowed vessels patent, while fissure, rupture, or hemorrhagic dissection of plaque may precipitate occlusive thrombosis.
Subject(s)
Platelet Adhesiveness , Thrombosis/physiopathology , Animals , Aorta/analysis , Aorta/ultrastructure , Arteriosclerosis/complications , Arteriosclerosis/physiopathology , Blood Platelets/physiology , Blood Platelets/ultrastructure , Endothelium, Vascular , Microscopy, Electron , Perfusion/methods , Rabbits , Regional Blood Flow , Thrombosis/etiologySubject(s)
Aspirin/adverse effects , Tooth Erosion/etiology , Adolescent , Adult , Arthritis, Juvenile/drug therapy , Child , Child, Preschool , Female , Humans , MaleSubject(s)
Anesthesia, Dental , Dentistry, Operative , Electrocardiography , Pulse , Anesthesia, Conduction , Anesthesia, Local , Bradycardia/etiology , Child , Dental Amalgam , Dental Cavity Preparation , Female , Humans , Lidocaine/pharmacology , Male , Pulse/drug effects , Stress, Psychological , Tachycardia/etiologySubject(s)
Dentist-Patient Relations , Pediatric Dentistry , Adolescent , Attitude to Health , Child , Child, Preschool , Humans , Iatrogenic Disease , Motivation , Oral Health , Parent-Child RelationsABSTRACT
Manejo del paciente niño y de sus padres. Medicación equilibrada: una auda para el niño en asistencia odontológica. Hipnosis en paidodoncia. Aplicaciones de la psicología en paidodoncia. Procednecia de examen bucal y plan de tratamiento en paidodoncia. Técnicas radiográficas para niños. Examen físico del niño. Educación sanitaria dental para el niño y sis padres. Medidas preventivas para el control de la caries dental. procedimientos operatorios aceptables en dientes primarios. Orificaciones proximales en dientes anteriores permanentes. Prevención y tratamiento de los traumatismos de los dientes anteriores permanentes. Patología de la pulpa dental. Terapéutica pulpar en dientes primarios y en permanentes inmaduros. Técnicas protéticas apropiadas para arcos en crecimiento. Tratamiento de la caries dental irrestricta ("rampante") en los niños. lesiones periodontales en los niños. Hábitos. Mantenimiento de los espacios. Maloclusiones menores e irregularidades de los Arcos. Atención dental del niño enfermo y disminuido
Subject(s)
Child , Pediatric Dentistry , PsychologyABSTRACT
Manejo del paciente niño y de sus padres. Medicación equilibrada: una auda para el niño en asistencia odontológica. Hipnosis en paidodoncia. Aplicaciones de la psicología en paidodoncia. Procednecia de examen bucal y plan de tratamiento en paidodoncia. Técnicas radiográficas para niños. Examen físico del niño. Educación sanitaria dental para el niño y sis padres. Medidas preventivas para el control de la caries dental. procedimientos operatorios aceptables en dientes primarios. Orificaciones proximales en dientes anteriores permanentes. Prevención y tratamiento de los traumatismos de los dientes anteriores permanentes. Patología de la pulpa dental. Terapéutica pulpar en dientes primarios y en permanentes inmaduros. Técnicas protéticas apropiadas para arcos en crecimiento. Tratamiento de la caries dental irrestricta ("rampante") en los niños. lesiones periodontales en los niños. Hábitos. Mantenimiento de los espacios. Maloclusiones menores e irregularidades de los Arcos. Atención dental del niño enfermo y disminuido
Subject(s)
Pediatric Dentistry , Child , PsychologyABSTRACT
Manejo del paciente niño y de sus padres. Medicación equilibrada: una auda para el niño en asistencia odontológica. Hipnosis en paidodoncia. Aplicaciones de la psicología en paidodoncia. Procednecia de examen bucal y plan de tratamiento en paidodoncia. Técnicas radiográficas para niños. Examen físico del niño. Educación sanitaria dental para el niño y sis padres. Medidas preventivas para el control de la caries dental. procedimientos operatorios aceptables en dientes primarios. Orificaciones proximales en dientes anteriores permanentes. Prevención y tratamiento de los traumatismos de los dientes anteriores permanentes. Patología de la pulpa dental. Terapéutica pulpar en dientes primarios y en permanentes inmaduros. Técnicas protéticas apropiadas para arcos en crecimiento. Tratamiento de la caries dental irrestricta ("rampante") en los niños. lesiones periodontales en los niños. Hábitos. Mantenimiento de los espacios. Maloclusiones menores e irregularidades de los Arcos. Atención dental del niño enfermo y disminuido
