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Biomedical subjects

A Ordinas

Publications and source records attributed to A Ordinas.

194 records · Page 11Linked to original sources
PubMed1976

Inhibition of human platelet aggregation by the proteolytic effect of streptokinase. Role of the human factor-VIII-related protein.

Defective ADP-induced aggregation was observed in in vitro streptokinases(SK)-treated normal platelet-rich plasma. Classic haemophilia and normal platelet poor plasma (PPP) treated with SK inhibit the aggregation of washed platelets; plasmin-treated normal human serum also shows an inhibitory effect on platelet aggregation. However, SK-treated von Willebrand plasmas do not inhibit the aggregation of washed platelets. This confirms the fact that the anti-aggregating effect is mainly linked to the digested factor VIII) but not to the digested fibrinogen. Defective ristocetin-induced platelet aggregation has also been observed in SK-treated plasmas. The presence of normal PPP does not modify the inhibition of the ADP-induced aggregation of washed platelets in SK-treated PPP. However, it does correct the ristocetin-induced aggregation. These results suggest that the inhibition of the ADP-induced aggregation is caused by the factor VIII degradation products, while the inhibition of the ristocetin-induced aggregation appears because of a defective von Willebrand activity of the factor VIII molecule.

Adenosine Diphosphate↗
PubMed1975

Interaction of platelets with purified macromolecules of the arterial wall.

A method is described for the study of the interaction between human blood platelets and intercellular matrix macromolecules of connective tissues such as those found in the sub-endothelium. The method is based on the qualitative and quantitative evaluation of the elution pattern of a platelet suspension from a mixed Sepharose 2B-fibrous protein column containing standardized amounts of fibrous proteins such as elastin or structural glycoprotein-microfibrils (SGP-MF). No interaction could be demonstrated with this method between platelets and SGP-MF but there was a very distinct interaction between platelets and elastin fibers. This could be confirmed by direct microscopical demonstration of platelet clusters around elastin fibers in cryostat sections of the affinity column.

Arteries↗
PubMedDate not supplied

Experimental basis for the use of red cell transfusion in the management of anemic-thrombocytopenic patients.

The Baumgartner perfusion technique was used as an experimental model to study the combined influence of red cell (RBC) and platelet counts on the interaction of platelets with the subendothelium. At normal hematocrit and a platelet count of 100,000 per microliter, platelet adhesion and platelet aggregate (PAG) formation on subendothelium were statistically decreased. At lower platelet counts (50,000/microliter), there was an even more marked reduction in the formation of PAGs. The critical role of RBCs was demonstrated in experiments at low hematocrit; the formation of PAGs was impaired in perfusions at 20 percent hematocrit at any platelet count tested. Platelet deposition on subendothelium was almost absent at 50,000 platelets per microliter, suggesting a negative synergistic effect for the association of low hematocrit (20%) with a low platelet count. Perfusion experiments carried out with nonanticoagulated blood drawn directly from anemic patients with mild thrombocytopenia (43,000-58,000 platelets/microliter) before and after RBC transfusion were in agreement with previous experiments that indicated that normalization of both platelet count and hematocrit is required to achieve optimum hemostasis. Our data give experimental support for the transfusional management of patients with anemia and thrombocytopenia.

Anemia↗
PubMedDate not supplied

Preparations of synthetic phospholipids promote procoagulant activity on damaged vessels: studies under flow conditions.

BACKGROUND: The possibility of developing synthetic platelet substitutes that could promote hemostasis with prolonged shelf-life and increased safety is an appealing one. STUDY DESIGN AND METHODS: Preparations containing synthetic phospholipids were incorporated into blood samples (1.15 mg/mL) in which platelets and white cell counts had been experimentally reduced by a filtration procedure. Vesicles containing phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylserine (PS), phosphatidylinositol (PI), or combinations of PC and PE and of PC and PS were tested in this system. Blood was recirculated (10 min; shear rate, 250/sec) through a perfusion chamber containing vascular segments. The ability of the various phospholipid preparations to promote fibrin formation on the damaged subendothelium was evaluated morphometrically and expressed as the percentage of fibrin coverage. Generation of thrombin in the system was monitored through the measurement of prothrombin fragments 1 and 2. RESULTS: Vesicles containing PC, PI, PE:PC (1:1), or PS:PC (1:3) increased fibrin deposition on the subendothelium (64.5 +/- 9.8%, 32.7 +/- 6.3%, 58.3 +/- 6.5%, and 46.6 +/- 15.2%, respectively; p < 0.01 vs. 11.5 +/- 1.2% in thrombocytopenic blood). Vesicles containing PE, PS, or PS:PC (3:1) did not show procoagulant effect. CONCLUSION: Synthetic phospholipid preparations promote a local procoagulant activity at sites of vascular damage when they are incorporated into thrombocytopenic blood maintained under flow conditions.

Animals↗
PubMedDate not supplied

Digital image analysis of platelet-extracellular matrix interactions: studies in von Willebrand disease patients and aspirin-treated donors.

We have developed an automated image analysis method which provides en face morphometric evaluation of platelet interactions with coverslips coated with extracellular matrices. This procedure gives also additional information on the intensity of platelet-surface interactions in the same specimens. To standardize the method, anticoagulated human blood was flowed at 800 s-1 during 10 min at 37 degrees C through a parallel perfusion chamber in which extracellular matrix (ECM)-coated coverslips were placed. The sensitivity of the new method was tested in similar studies performed in patients with von Willebrand disease or treated with aspirin (500 mg/day). The extent of platelet deposition on the ECMs was evaluated by both standard and new morphometric procedures. Coverslips were successively embedded in resin and processed for cross-sectional analysis and results were compared with those provided by the new automated procedure. A good correlation was found between results of covered surface obtained by both methods (r = 0.86; p < 0.005). Results from perfusions performed with blood from patients with platelet defects confirmed the correspondence of grey levels in the digitized images with the heights of groups of interacting platelets calculated from cross sections. The new automated method, in only one stage, allows a reliable evaluation of the global interaction of platelets with the ECM and effectively detected qualitative modifications in platelet-platelet interactions in patients with known platelet defects. The method described could be applied to the evaluation of the interactions of platelets with purified components of the subendothelium.

Aspirin↗
PubMedDate not supplied

Platelet adhesion to exposed endothelial cell extracellular matrixes is influenced by the method of preparation.

The relative thrombogenicity of extracellular matrixes (ECMs) produced by cultured human umbilical endothelial cells (ECs) was studied under flow conditions. ECMs were prepared using a number of physical and chemical methods, and their reactivity toward platelets was morphometrically evaluated. von Willebrand factor (vWF), fibronectin (FN), and 13-hydroxy-9-cis,11-trans-octadecadienoic acid (13-HODE) were also determined. We found that platelet adhesion to ECMs differed significantly, both quantitatively and qualitatively, with the method of ECM preparation. Mechanically prepared ECM exposed a less thrombogenic surface compared with ECM prepared by chemical methods (platelet-covered surface of 20% and 50%, respectively). Evaluation of the ECM components vWF, FN, and 13-HODE showed significant changes, both in their concentrations and distribution patterns, depending on the method of ECM preparation. The decrease measured in the levels of ECM-associated vWF (from 108 to 9.2 ng/10(4) cells) and the minor changes observed in the distribution pattern of subendothelial FN did not appear to be sufficient to explain the altered platelet adhesion observed in our model. This suggests that the amount of 13-HODE probably associated to the remaining ECs present in the mechanically exposed ECM could be one factor that specifically contributed to the nonthrombogenic state of these preparations. We conclude that the degree of ECM reactivity toward platelets is dependent on the method of ECM preparation and that this is related to the removal of specific EC/ECM components that modulate their thromboresistant/thrombogenic properties. This fact should be taken into account when ECMs produced by cultured ECs are used in platelet adhesion studies.

Antithrombins↗
PubMedDate not supplied

Effect of anticoagulants on activation of polymorphonuclear leukocytes induced by shear stress.

We analyzed how actin polymerization, CD11b expression and homotypic aggregation could be used as markers to study leukocyte activation. Leukocytes were obtained from blood anticoagulated with: citrate, unfractioned heparin (UH) and low molecular weight heparin (LMWH). Flow cytometry was used to study actin polymerization and expression of CD11b after leukocyte exposure to shear stress. Leukocyte aggregation was microscopically assessed. Shear increased both actin polymerization and expression of CD11b in citrated blood (100.1&#x00B1;7.1 vs. 85.8&#x00B1;8.5 p&#x003C; 0.05 and 53.5&#x00B1;3.5 vs. 20.7&#x00B1;5.1; p&#x003C; 0.005 respectively). These parameters remained unmodified in UH samples. Using both anticoagulants together, we observed increase in CD11b expression induced by shear stress (59.3&#x00B1;2.1 vs. 25.1&#x00B1;11.0; p&#x003C; 0,05). LMWH samples showed higher basal levels of actin polymerization and CD11b expression than citrated samples (237&#x00B1;40.8, vs. 85.8&#x00B1;8.5 p&#x003C; 0.05 and 47.8&#x00B1;2.6, vs. 20.7&#x00B1;5.1; p&#x003C; 0.005) but no changes induced by shear were observed. When LMWH was used in combination with citrate we observed a decrease in basal activation and significant modifications in CD11b expression induced by shear stress (80.0&#x00B1;4.1 vs. 50.4&#x00B1;2.7). Leukocyte aggregation was modified by UH at basal levels and by LMWH after shear stress. These results indicate that exposure to shear stress results in leukocyte activation. The choice of anticoagulant is a crucial factor in studies of leukocyte function.

Journal Article↗
PubMedDate not supplied

Isotype distribution and clinical significance of antibodies to cardiolipin, phosphatidic acid, phosphatidylinositol and phosphatidylserine in systemic lupus erythematosus: prospective analysis of a series of 92 patients.

OBJECTIVE: To determine the prevalence and correlation with clinical manifestations of the IgG and IgM isotypes of antibodies to cardiolipin (aCL), phosphatidic acid (aPA), phosphatidylinositol (aPI) and phosphatidylserine (aPS) in patients with systemic lupus erythematosus (SLE). METHODS: Clinical and laboratory features of 92 consecutive unselected patients with SLE were prospectively studied over two years. aCL, aPA, aPI and aPS were determined by ELISA. RESULTS: aCL were detected in 34 (37%) patients, aPA in 26 (28%), aPI in 22 (24%), and aPS in 29 (32%). A significant association was found between the appearance of thrombosis and the presence of IgG aCL (p < 0.001) and IgG aPS (p < 0.05). A significant association was also found between thrombocytopenia and the presence of IgG aCL (p < 0.001), IgG aPA (p < 0.01), IgG aPI (p < 0.05), and IgG aPS (p < 0.001). The development of hemolytic anemia was associated with the detection of IgM aCL (p < 0.001), IgM aPA (p < 0.05), IgM aPI (p < 0.001), and IgM aPS (p < 0.01). CONCLUSION: We found a relatively high prevalence of aCL, aPA, aPI and aPS in our SLE population and confirmed the presence of a correlation between the IgG isotype of these antibodies and thrombosis and thrombocytopenia, and also between the IgM isotype and hemolytic anemia. These results demonstrate the variety of antiphospholipid antibodies that can be detected in SLE patients, as well as their association with the clinical manifestations of the antiphospholipid syndrome.

Adolescent↗
PubMedDate not supplied

Inhibition of fibrin deposition on the subendothelium by a monoclonal antibody to polymorphonuclear leukocyte integrin CD11b. Studies in a flow system.

BACKGROUND AND OBJECTIVE: The development of prothrombotic and procoagulant states may be regulated by direct platelet-leukocyte contact mediated by membrane receptors. We have investigated the role of CD11b integrin in polymorphonuclear leukocytes (PMN) on fibrin formation and platelet reactivity with vascular subendothelium. METHODS: Studies were carried out following a well-established perfusion model, employing either citrated blood, where fibrin formation is blocked, or blood anticoagulated with low molecular weight heparin, which allows thrombin and fibrin formation. Isolated PMN or platelets were treated with specific monoclonal antibodies to CD11b or to CD62P, respectively, and incorporated in reconstituted blood. RESULTS: Treatment of PMN with anti-CD11b significantly decreased the percentage of surface covered with a thick layer (> 5 microns) of fibrin (34.8 +/- 3.3% vs 53.3 +/- 4.9% in control, p < 0.05); it also reduced the average height of fibrin layer and the number of adherent leukocytes (7.9 +/- 1.2 microns vs 10.6 +/- 1.4 microns in control, p < 0.05; and 87 +/- 8 PMN/mm2 vs 186 +/- 25 PMN/mm2 in control, p < 0.05) respectively. Treatment of PMN with CD11b did not significantly affect the attachment of platelets onto the subendothelium when using citrated blood, though a slight decrease in platelet adhesion was observed in the heparinized samples. Treatment of platelets with anti-CD62P did not significantly modify any of the parameters studied. INTERPRETATION AND CONCLUSIONS: Our results indicate that PMN have a role in promoting fibrin deposition under flow conditions, through the participation of CD11b integrin. Under our experimental conditions, this effect does not seem to be influenced by CD62P expressed on activated platelets.

Animals↗