Biomedical subjects

A Ordinas

Publications and source records attributed to A Ordinas.

At least 37 records · Page 2Linked to original sources

PubMed2001

Comparison of the effects of human erythrocyte ghosts and intact erythrocytes on platelet interactions with subendothelium in flowing blood.

We investigated whether ghosts behaved similarly to intact erythrocytes to maintain regular primary hemostasis under flow conditions. To this end we performed perfusion experiments with whole blood in which erythrocytes were replaced by pink ghosts, and platelet interaction with the subendothelial surface of a damaged vessel was morphometrically evaluated. The same objective was sought by means of studies with a platelet function analyzer (PFA-100(TM) instrument). Perfusions performed with control blood reconstituted with intact erythrocytes gave rise to 0.4+/-0.2% contact but not spread platelets, 10.8+/-3.4% adhering and spread platelets, 16.3+/-4.6% platelets in thrombi, with 27.5+/-7.4% of the surface covered. Even though the average diameter of the ghosts was smaller than that of intact erythrocytes (5.3 microm vs. 7.7 microm), the values obtained in perfusions performed with ghosts were similar to those of the erythrocyte controls. Studies performed with the PFA-100(TM) analyzer were consistent with those observed in perfusion studies. The viscosity of control blood was compared with that of blood reconstituted with ghosts. At shear rates lower than 450 s(-1), the viscosity of the ghost samples was higher than that of the controls, but the difference progressively decreased as shear rate increased up to 750 s(-1) (3.61+/-0.15 and 3.71+/-0.17 cP, respectively). In conclusion, the results of our study showed that ghosts behaved similarly to intact erythrocytes in maintaining a normal platelet interaction with digested subendothelium, under conditions of moderate shear rate and constant hematocrit (40%). The rheological activity of ghosts, bodies that are metabolically less active, was sufficient for them to satisfactorily act as substitutes for intact erythrocytes in our system.

Blood Viscosity↗

PubMed2000

Antiplatelet effects of sodium nitroprusside in flowing human blood: studies under normoxic and hypoxic conditions.

We explored the ability of sodium nitroprusside to modify adhesive and cohesive function of platelets in flowing blood, under normoxic and hypoxic conditions. Aliquots of both untreated and sodium nitroprusside-treated blood were prepared for studies of: (1) platelet aggregation in plasma; (2) erythrocyte deformability; (3) platelet interaction with damaged subendothelium, by using a well-defined perfusion system; and (4) blood gasometry in the perfused samples. Results showed that sodium nitroprusside-treated blood always showed a totally inhibited arachidonic acid-induced platelet aggregation in plasma, as well as significantly increased erythrocyte deformability (0.44+/-0.09 up to 0.66+/-0.05; p<0.05). However, treatment with sodium nitroprusside did not modify the pattern of platelet interaction with subendothelium (percentage of contact, adhesion, thrombus, and covered surface) with respect to untreated blood, under any of the shear rates used (300, 800, and 1800 seconds(-1)), although it significantly reduced the height of thrombi (9.8+/-0.4 vs. 8.3+/-0.4 microm; p<0.05). Hypoxic conditions did not have a noticeable effect in modifying antiplatelet effects of sodium nitroprusside. Additionally, the presence of sodium nitroprusside impaired the normal oxygenation of the blood during perfusion. pO2 in control untreated samples rose from 40.3+/-5.0 mm Hg perfusions to 100.4+/-12.5 mm Hg but remained at 66.3+/-6.3 mm Hg in sodium nitroprusside-treated blood (p<0.05). Our results did not show a significant effect of sodium nitroprusside in the modulation of platelet interaction with subendothelium. The marginal reduction in the thrombi height could be related to rheological interference of increased erythrocyte deformability.

Blood Gas Analysis↗

PubMed2000

The 4G/5G polymorphism of the type 1 plasminogen activator inhibitor gene and thrombosis in patients with antiphospholipid syndrome.

OBJECTIVE: To investigate the relationship between the 4G/5G polymorphism of the type 1 plasminogen activator inhibitor (PAI-1) gene and thrombotic manifestations in patients with antiphospholipid syndrome (APS). METHODS: We studied a total of 247 patients included in the following 4 groups: 70 patients with primary APS, 104 patients with systemic lupus erythematosus (40 with antiphospholipid antibodies [aPL] and clinical [secondary] APS, 13 with aPL but without clinical APS, and 51 with neither detectable aPL nor a history of thrombosis), 14 asymptomatic individuals with aPL, and 59 patients with thrombosis but without known thrombosis risk factors. A control group of 100 healthy individuals was also analyzed. PAI-1 4G/5G polymorphism was determined by polymerase chain reaction and endonuclease digestion. RESULTS: The allele frequency of 4G/5G in controls was 0.47/0.53. There were no differences in allele distribution among patient groups or between patients and controls. However, a higher frequency of the 4G allele was observed in APS patients with versus those without thrombosis (0.57 versus 0.39; P < 0.05) (odds ratio [OR] 2.83, 95% confidence interval [95% CI] 1.18-6.76). This higher frequency of the 4G allele was attributable to the higher frequency in patients with versus those without arterial thrombosis (0.64 versus 0.43; P < 0.01) (OR 5.96, 95% CI 1.67-21.32), while patients with venous thrombosis had an allele distribution similar to that of those without venous thrombosis (0.49 versus 0.50; P not significant). There was a trend toward higher PAI-1 antigen and activity levels in APS patients and controls with the 4G/4G genotype, but this did not reach statistical significance. CONCLUSION: The presence of the 4G allele of the 4G/5G polymorphism of the PAI-1 gene may be an additional risk factor for the development of arterial thrombosis in APS.

Adult↗

PubMed2000

Abnormal platelet cytoskeletal assembly in hemodialyzed patients results in deficient tyrosine phosphorylation signaling.

BACKGROUND: Uremic patients have a bleeding tendency associated with a platelet dysfunction. We evaluated the impact of a repeated hemodialysis procedure on primary hemostasis by analyzing different aspects of platelet activation in uremic patients. METHODS: Studies were performed in (1) eight patients with end-stage renal disease before the hemodialysis program was initiated and after initiating hemodialysis treatment, and in (2) eight patients on maintenance hemodialysis who were transferred to continuous ambulatory peritoneal dialysis. Studies included routine platelet aggregations and evaluation of platelet-subendothelium interactions under flow conditions. Contractile proteins and tyrosine phosphorylation associated with the cytoskeleton were analyzed, before and after thrombin activation of platelets, by electrophoresis after Triton X-100 extraction. RESULTS: No changes in the clinical parameters analyzed were observed among the different study groups. Aggregation and platelet adhesion only improved when patients were shifted from hemodialysis to continuous ambulatory peritoneal dialysis (P < 0.05 for both percentage of surface covered by platelets and aggregate formation). The association of cytoskeletal proteins in platelets from patients under hemodialysis treatment was statistically decreased with respect to the corresponding values in platelets from patients not subjected to dialysis (P < 0.01 for actin). However, after two months on peritoneal dialysis, these values increased to almost control values (P < 0.001 for actin, vs. hemodialysis). Similarly, translocation of tyrosine-phosphorylated proteins to the cytoskeletal fraction was impaired in platelets from hemodialyzed patients, and it recovered partially after the patients transferred to continuous ambulatory peritoneal dialysis. CONCLUSIONS: Our present data support the concept that repeated platelet stress during hemodialysis has a deleterious effect on the organization of platelet cytoskeleton, which seems to impair the translocation of signal transduction proteins within platelets compromising the platelet function in uremia.

Adult↗

PubMed2000

Effects of the addition of second-messenger effectors to platelet concentrates separated from whole-blood donations and stored at 4 degrees C or -80 degrees C.

BACKGROUND: Platelet concentrates (PCs) are currently stored at 22 degrees C under continuous agitation. Because of the potential risk of the overgrowth of bacteria in case of contamination, PC shelf life is limited to 5 days. A mixture of second-messenger effectors is being evaluated to determine if it has benefits for cold liquid storage and cryopreservation of platelets. STUDY DESIGN AND METHODS: PCs separated from whole-blood donations by the buffy coat method were randomly assigned (n = 6 each) to be stored for 5 days at 22 degrees C under continuous agitation or at 4 degrees C after treatment with a platelet storage medium (ThromboSol, LifeCell Corp. ). PCs were also cryopreserved with 6-percent DMSO (final concentration) or with ThromboSol plus 2-percent DMSO (final concentration) (TC). After storage, platelets were analyzed by flow cytometry, transmission electron microscopy, and aggregation and perfusion techniques. RESULTS: Cold liquid storage of ThromboSol-treated platelets resulted in a lower binding of coagulation factor Va on the platelet surface than on platelets stored at 22 degrees C. In transmission electron microscopy, a conversion to spherical morphology was seen in the case of cold liquid storage. No difference between ThromboSol-treated platelets stored at 4 degrees C and platelets stored at 22 degrees C was seen in perfusion studies. Cryopreservation in the presence of TC prevented the reduction in glycoprotein Ib and IV expression on platelet surface that is seen in 6-percent DMSO-cryopreserved platelets. Platelets cryopreserved in TC covered, by thrombus, a significantly greater percentage of the perfused surface after the freezing and thawing process. CONCLUSION: ThromboSol-treated PCs separated from whole-blood donations by the buffy coat method, stored at 4 degrees C for 5 days, or cryopreserved in the presence of TC, maintained in vitro functional activity comparable to that achieved by current methods of storage, although discoid morphology was not preserved during cold liquid storage with ThromboSol.

Bacteria↗

PubMed2000

Alterations in cytoskeletal organization and tyrosine phosphorylation in platelet concentrates prepared by the buffy coat method.

BACKGROUND: Numerous morphologic and biochemical changes occurring during platelet storage may result in the impairment of platelet function. STUDY DESIGN AND METHODS: The effect of preparation and storage conditions on platelet function was analyzed through evaluation of cytoskeletal organization and signaling mechanisms involved in the activation of platelets by thrombin. Samples of platelets prepared by the buffy coat method were obtained before and after the platelet concentrates were prepared during storage for 1, 3, and 5 days. Thrombin-induced aggregation was monitored, and changes in the organization of proteins in the cytoskeleton were analyzed by gel electrophoresis. For the analysis of tyrosine phosphorylation, proteins were transferred to nitrocellulose membranes and probed with a specific antibody. RESULTS: The aggregation and the cytoskeletal organization induced by thrombin activation were markedly impaired immediately after preparation of platelet concentrates, although they normalized after the first 24 hours of storage and decreased progressively after 3 days of storage. Results in tyrosine phosphorylation paralleled those obtained with cytoskeletal organization, except for samples obtained immediately after processing to obtain platelet concentrates. CONCLUSION: These data indirectly suggest that the stress induced by the preparation method has an activating effect on platelet function that may imply a delayed platelet response to further stimuli. This effect may result in a deficient redistribution of signaling molecules within platelets.

Blood Platelets↗

PubMed2000

Infusible platelet membranes improve hemostasis in thrombocytopenic blood: experimental studies under flow conditions.

BACKGROUND: The potential hemostatic effect of infusible platelet membranes (IPM; Cyplex, Cypress Bioscience) prepared from outdated human platelets is investigated. STUDY DESIGN AND METHODS: Increasing concentrations of IPM were added to blood samples anticoagulated with low-molecular-weight heparin, in which platelets and WBC counts had been experimentally reduced by a filtration procedure. Thrombocytopenic blood with IPM was circulated in a perfusion chamber at various shear rates (300, 600, and 1200/sec(-1)), and platelet and fibrin deposition on the surface of a damaged vessel was measured. Prothrombin fragments 1 and 2 (F1+2) levels were also monitored. RESULTS: Under conditions of severe thrombocytopenia (<6000 platelets/microL) IPM did not increase platelet deposition. However, a dose-dependent increase in fibrin deposition was observed with concentrations of IPM ranging from 0.5 to 2 mg per kg in perfusions at 300 and 600 per sec(-1) (p<0.05 vs. thrombocytopenic blood). Experimental studies performed under conditions of moderate thrombocytopenia and higher shear rates (25, 000-30,000 platelets/microL; at 600 and 1200/sec(-1)) showed that IPM concentrations equivalent to 0.5 or 1 mg per kg improved fibrin deposition (33.5 +/- 9.5% and 37.7 +/- 12.8%, respectively, vs. 22.7 +/- 5.2% in controls) and also promoted a moderate increase in platelet deposition, with a concomitant significant increase in the size of platelet aggregates (p<0.05). Exposure of thrombocytopenic blood to a damaged vessel resulted in an increase of F1+2 levels from 0.8 +/- 0.15 to 1.7 +/- 0.22 nM at 300 per sec(-1) and 1.94 +/- 0.46 nM at 600 per sec(-1). Postperfusion levels of F1+2 after the addition of IPM were always similar to levels in untreated controls. CONCLUSION: IPM promotes local procoagulant activity at sites of vascular damage under conditions of severe and moderate thrombocytopenia. IPM also appears to facilitate platelet cohesive functions under conditions of moderate thrombocytopenia.

Blood Platelets↗

PubMed2000

Adherence of platelets under flow conditions results in specific phosphorylation of proteins at tyrosine residues.

Collagen is a powerful platelet activating agent that promotes adhesion and aggregation of platelets. To differentiate the signals generated in these processes we have analyzed the tyrosine phosphorylation occurring in platelets after activation with collagen in suspension or under flow conditions. For the suspension studies, washed platelets were activated with different concentrations of purified type I collagen (ColI). Studies under flow conditions were performed using two different adhesive substrata: ColI and endothelial cells extracellular matrix (ECM). Coverslips coated with ColI or ECM were perfused through a parallel-plate perfusion chamber at 800 s(-1) for 5 min. After activation of platelets either in suspension or by adhesion, samples were solubilized and proteins were resolved by electrophoresis. Tyrosine-phosphorylated proteins were detected in immunoblots by specific antibodies. Activation of platelet suspensions with collagen induced tyrosine phosphorylation before aggregation could be detected. Profiles showing tyrosine-phosphorylated proteins from platelets adhered on ColI or on ECM were almost identical and lacked proteins p95, p80, p66, and p64, which were present in profiles from platelets activated in suspension. The intensity of phosphorylation was quantitatively weaker in those profiles from platelets adhered on ECM. Results from the present work indicate that activation of platelets in suspension or by adhesion induces differential tyrosine phosphorylation patterns. Phosphorylation of proteins p90 and p76 may be related to early activation events occurring during initial contact and spreading of platelets. Considering that adhesion is the first step of platelet activation, studies on signal transduction mechanisms under flow conditions may provide new insights to understand the signaling processes taking place at earliest stages of platelet activation.

Blotting, Western↗

PubMed2000

Thrombin facilitates primary platelet adhesion onto vascular surfaces in the absence of plasma adhesive proteins: studies under flow conditions.

BACKGROUND AND OBJECTIVE: The effect of local and circulating thrombin on platelet adhesion onto vascular surfaces was explored in the absence of plasma adhesive proteins using flow conditions. DESIGN AND METHODS: To study the local effects of thrombin, denuded rabbit aorta segments were incubated with thrombin concentrations of 0.001, 0.01 and 0.1 U/mL. To evaluate the effects of circulating thrombin, the same concentrations were added to perfusates consisting of washed platelets and washed red blood cells suspended in a human albumin solution (5%). In some experiments, purified von Willebrand's factor (vWF) (Haemate-P) was added to the perfusates (0. 8 U/mL of vWF, final concentration). A humanized chimeric antibody to the GPIIb-IIIa complex (Reopro) was used to determine the role of this glycoprotein on platelet adhesion under the conditions described. The effect of blocking GPIb was also assessed. Perfusions were carried out at 800 s(-1) for 10 min. The interaction of platelet with the vessel surface was morphometrically evaluated and expressed as percentage of surface coverage (%SC). Changes in the surface expression of the major platelet antigens were also analyzed by flow cytometry. RESULTS: Incubation of subendothelial surfaces with thrombin enhanced platelet deposition with respect to control levels (increases in SC of 64%, 79% and 86% with 0.001, 0.01 and 0.1 U/mL of thrombin, respectively). Low concentrations of thrombin (0.001 and 0.01 U/mL) incorporated in the perfusates resulted in a similar pro-adhesive effect (increases in SC of 64% and 71%, respectively) while the highest concentration (0.1 U/mL) failed to produce a pro-adhesive effect due to the augmented formation of platelet aggregates with subsequent thrombocytopenia (15+/-1 vs. 160+/-5x10(9) plt/L in the perfusates). Similar results were obtained when VWF was present in the perfusate. Reduction of platelet deposition by blockade of GPIIb-IIIa (to 5.3+/-0.7%) was partially restored by thrombin. Blockade of GPIb prevented platelets from adhering even when thrombin was present (%SC of 2.0+/-0.8%). No significant changes in the distribution of platelet membrane glycoproteins during perfusion experiments were detected. INTERPRETATION AND CONCLUSIONS: Our results suggest that thrombin facilitates primary platelet adhesion onto vascular surfaces even in the absence of plasma adhesive proteins. This effect seems to be mainly dependent on the GPIb/vWF axis.

Animals↗

PubMed2000

Differential aspects of the glycoprotein Ib-von Willebrand factor axis in human and pig species.

BACKGROUND AND OBJECTIVE: The role of glycoprotein Ib (GPIb) in platelet adhesion to subendothelium is well established in human species. However, the interaction of GPIb and von Willebrand factor (VWF) in a widely used experimental model in thrombosis research, that of the pig, has not been clearly elucidated. We investigated the differences between human and pig species in the GPIb/VWF axis in several ways. DESIGN AND METHODS: Standard aggregometry and perfusion studies with circulating blood were applied to isolated platelets or to blood reconstituted with isolated platelets, VWF and red blood cells from the different species. Platelet aggregation to VWF in the presence of either ristocetin or botrocetin was tested. RESULTS: Human VWF and ristocetin did not agglutinate pig platelets. However, botrocetin was capable of agglutinating pig platelets. In perfusion studies (800 s(-1), 10 min), washed platelets from both species were suspended in albumin solutions containing human VWF (hVWF) or porcine VWF (pVWF) and red blood cells from the corresponding species. Reconstituted blood with high concentrations of pVWF (> or =0.25 U/mL) caused severe thrombocytopenia during the perfusion procedure when added to human platelets. Nevertheless, lower concentrations (< or =0.1 U/mL) promoted the formation of large aggregates. Under our experimental conditions, hVWF poorly supported pig platelet adhesion. INTERPRETATION AND CONCLUSIONS: In conclusion, pVWF may support human platelet adhesion and even promote aggregation, while hVWF can only partially facilitate pig platelet adhesion. Minimal concentrations of pVWF could facilitate the interaction of human platelets with subendothelium, increasing their adhesive and aggregating capabilities. Understanding the molecular differences of the GPIb-VWF axis in different species may prove useful for developing therapeutic strategies aimed at preventing excessive platelet deposition on damaged vascular surfaces.

Animals↗

PubMed2000

Prevalence and clinical significance of antiprothrombin antibodies in patients with systemic lupus erythematosus or with primary antiphospholipid syndrome.

BACKGROUND AND OBJECTIVE: Antibodies to prothrombin (aII) have been identified in patients with antiphospholipid antibodies, but their clinical significance is not well known. The aim of our study was to investigate their prevalence and association with clinical manifestations of the antiphospholipid syndrome (APS) in patients with primary APS or with systemic lupus erythematosus (SLE). DESIGN AND METHODS: A series of 177 patients with autoimmune diseases was studied: 70 with primary APS and 107 with systemic lupus erythematosus. A control group of 87 healthy volunteers were included in the study. aII were investigated in sera by an ELISA, using human prothrombin as antigen fixed in irradiated polystyrene plates. RESULTS: aII prevalence in patients with autoimmune disease was 47% (57% and 40% in patients with primary APS or with SLE, respectively) significantly higher than in controls (5%) (p<0.0001). In the whole series, thrombotic events were more prevalent in patients with aII (45% vs 28%; p=0.02). Moreover, aII was found to be an independent risk factor for arterial thrombosis (OR=2.4; p=0. 04). Similarly, in patients with SLE, aII were associated with both arterial and venous thrombosis (35% vs 14%; p=0.01), although only IgG-aII (OR=3.7; p=0.01) had an independent value as risk factor for thrombosis. However, a relationship between aII and thrombosis was not found in primary APS. aII were associated with thrombocytopenia only in patients with primary APS (OR=6.7; p=0.007). INTERPRETATION AND CONCLUSIONS: aII seem to be a serological marker of thrombosis in autoimmune diseases, mainly in SLE patients and/or in the arterial territory.

Abortion, Spontaneous↗

PubMed1999

Ex vivo response to aspirin differs in stroke patients with single or recurrent events: a pilot study.

The dose of aspirin for secondary stroke prevention and the clinical meaning of ex vivo platelet abnormalities are debated. We assessed prospectively 39 noncardioembolic stroke patients in which 300 mg/day aspirin had proved effective (n=24) or ineffective (n=15) to prevent recurrent ischemic events. We evaluated platelet aggregation induced by arachidonic acid, adenosine diphosphate and epinephrine, and the sensitivity of platelets to increasing concentrations of the synthetic thromboxane mimetic U46619. Aggregation studies were repeated while subjects received 300 (study phase 1), and 600 (study phase 2) mg/day aspirin, respectively. Overall, arachidonic acid-induced platelet aggregation was less effectively inhibited during study phase 1 compared to phase 2. Arachidonic acid and epinephrine promoted a stronger platelet aggregation in aspirin nonresponders than in aspirin responders while taking 300 mg/day aspirin. On the other hand, 600 mg/day effectively inhibited platelet function in both clinical groups. A lower sensitivity to thromboxane receptors was also found during phase 1 of the study, although the response was similar between aspirin responders and nonresponders. This pilot study suggests that 300 mg/day aspirin is less effective than 600 mg/day to block the cyclooxygenase pathway in noncardioembolic stroke and, incomplete cyclooxygenase inhibition is associated with recurrent thromboembolic events despite adequate aspirin compliance. It is likely that patients could receive a more efficacious stroke prevention if the dose of aspirin is tailored to individual needs as reflected by laboratory findings.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗

PubMed1999

Modifications in accessibility of membrane glycoproteins, binding of specific ligands and coagulation factor V during the activation of platelets in blood emerging from bleeding time wounds.

Dual color flow cytometric techniques were applied to micro-aliquots of whole blood obtained from bleeding time (BT) wounds. Modifications in platelet activation markers (P-selectin [CD62P]) and lysosomal related protein (UMPS [CD63]), presence of membrane glycoproteins (GPIb [CD42b], GPIIb-IIIa [CD41a], GDIV [CD36], binding of von Willebrand factor (vWF), fibrinogen (Fg) and factor V [FV]) were analyzed in normal donors (n = 10) and in a severe von Willebrand patient (type 3) von Willebrand disease [vWD]). Samples of blood (20 microl) were sequentially removed from BT wound edges for up to 5 min and fixed with paraformaldehyde. Antigens were detected using the corresponding tagged monoclonal antibodies (moAbs) and quantitative results were referred to those found on platelet samples obtained from venous blood obtained from the same individuals. A progressive increase in % of platelets positive for activation dependent antigens (CD62 from 7 +/- 2 to 48 +/- 19% and CD63 from 9 +/- 1 to 44 +/- 8%; initial vs. 4 min) was observed. Accessibility of GPIIb-IIIa epitopes on platelets from BT wounds remained slightly above levels observed in venous blood platelets, despite a progressive increase in the presence of platelets positive for Fgn. Binding of MoAb to GPIV increased at late stages of BT. A moderate decrease in the binding of a moAb to GPIb was observed on platelets obtained at late stages of the BT (14 +/- 9% and 20 +/- 6% at 4 and 5 min, respectively). This apparent decrease in GPIb epitopes paralleled an increased presence of platelets positive for vWF (26 +/- 12 and 38 +/- 15%). Binding of moAb to GPIb always remained above basal levels in platelets obtained from BTs performed in the patient with type 3 vWD. FV levels on platelets coming from the BT persisted at background levels in all the individuals and at all times studied.

Antibodies, Monoclonal↗

PubMed1999

Clinical study and follow-up of 100 patients with the antiphospholipid syndrome.

OBJECTIVES: To study the clinical characteristics at diagnosis and during follow-up of patients with the antiphospholipid syndrome (APS) and to analyze the influence of treatment on their outcome. PATIENTS: One hundred patients with APS were included (86% female and 14% male; mean age, 36 years). Sixty-two percent had primary APS and 38% had APS associated with systemic lupus erythematosus (SLE). The median length of follow-up was 49 months. RESULTS: Fifty-three percent of the patients had thromboses, 52% had thrombocytopenia, and 60% of the women had pregnancy losses. Patients with APS associated with SLE had a higher prevalence of hemolytic anemia (P = .02), thrombocytopenia (platelet count lower than 100 x 10(9)/L) (P = .004), antinuclear antibodies (P = .0002), and low complement levels. Fifty-three percent of the patients with thrombosis had recurrent episodes (86% in the same site as the previous thrombotic event). Recurrences were observed in 19% of the episodes treated with long-term oral anticoagulation, in 42% treated prophylactically with aspirin, and in 91% in which anticoagulant/antiaggregant treatment was discontinued (P = .0007). Multivariate analysis showed that prophylactic treatment and older age had an independent predictive value for rethrombosis. Prophylactic treatment during pregnancy (usually with aspirin) increased the live birth rate from 38% to 72% (P = .0002). CONCLUSIONS: Patients with APS have a high risk of recurrent thromboses. Long-term oral anticoagulation seems to be the best prophylactic treatment to prevent recurrences. Prophylactic treatment with aspirin during pregnancy reduced the rate of miscarriages remarkably.

Adolescent↗

PubMed1999

Prevalence of hepatitis C virus infection in patients with antiphospholipid syndrome.

BACKGROUND/AIMS: The aim of this study was to determine the prevalence and clinical significance of hepatitis C virus (HCV) infection in patients with the antiphospholipid syndrome (APS). METHODS: A series of 88 consecutive patients (78 female and 10 male), with a mean age of 39 years (range 15-79), was prospectively studied. All patients had been diagnosed with APS: 54 (61%) primary APS and 34 (39%) APS associated with systemic lupus erythematosus. A group of 200 apparently healthly blood donors was included in the study. Anti-HCV antibodies were investigated in the serum of all patients using a third-generation ELISA and confirmed by recombinant immunoblot assay. RNA-HCV was investigated in anti-HCV positive samples by polymerase chain reaction. Anticardiolipin, anti-beta2-glycoprotein I and antiprothrombin antibodies were evaluated by ELISA. Lupus anticoagulant was studied by coagulometric assays. RESULTS: Only 2 (2.2%) patients showed positivity for anti-HCV antibodies, but none of them had clinical or biochemical signs of liver disease. Furthermore, RNA-HCV was not detected in serum of any of these patients. Lupus anticoagulant was positive in 57% of patients. Anticardiolipin antibodies were positive in 60% of patients, anti-beta2-glycoprotein I antibodies in 43% of patients, and antiprothrombin antibodies in 56% of patients. The prevalence of anti-HCV in blood donors was 1%. CONCLUSIONS: The prevalence of anti-HCV in patients with APS is low and similar to that in healthy people in our area. HCV infection does not seem to be involved in the etiopathogenesis of this syndrome.

Adolescent↗

PubMed1999

Platelet function during cardiac surgery and cardiopulmonary bypass with low-dose aprotinin.

OBJECTIVE: To determine whether two low-dose regimens of aprotinin influence platelet function. DESIGN: Prospective, randomized, single-blinded trial. SETTING: University teaching hospital performing 600 cardiac operations per year. PARTICIPANTS: Fifty-nine patients scheduled for cardiac surgery undergoing cardiopulmonary bypass (CPB) of expected duration of 60 minutes or more. INTERVENTIONS: Patients were randomized into three groups. Group C (control) included 21 patients who did not receive aprotinin. In group A2, 17 patients received 14,286 kallikrein inhibitor units (KIU)/kg (2 mg/kg) of aprotinin before surgery, followed by a continuous infusion of 7,143 KIU/kg/h (1 mg/kg/h) until the end of surgery. In group A4, 19 patients received 28,572 KIU/kg (4 mg/kg) of aprotinin before surgery, followed by the same infusion. MEASUREMENTS AND MAIN RESULTS: Postoperative bleeding and transfusion requirements were significantly less in group A4. Changes in platelet number and function were similar in the three groups. Platelet aggregation was assessed in four periods: before CPB (T1), post-CPB (T2), and 2 hours (T3) and 4 hours (T4) after CPB. Platelet aggregation induced by adenosine diphosphate, 1 and 2 micromol/L; ristocetin, 1 mg/mL; and arachadonic acid (AA), 1.4 mmol/L, decreased at T2 (p < 0.001) in all groups, and for the ristocetin and AA groups, remained at less than baseline values at T3 and T4. In five patients from each group, platelet receptors for glycoprotein IIb-IIIa (GPIIb-IIIa) and expression of platelet activation markers, guanosine monophosphate 140 (GMP-140) and lysosomal protein, were measured by flow cytometry before and after CPB. Modifications in the expression of GPIIb-IIIa were always modest and without statistical significance. Platelet activation markers, GMP-140 or lysosomal protein, nearly doubled from baseline to post-CPB only in the A4 group, whereas they remained stable in both other groups (statistically not significant). CONCLUSION: The two regimens of aprotinin, both considered low dosage, did not exert a protective effect on platelet function. Neither dose produced changes in platelet GPIIb-IIIa or platelet activation markers. However, bleeding and transfusion needs were decreased.

Adenosine Diphosphate↗

PubMed1999

Impaired antiplatelet effects of aspirin associated with hypoxia and ATP release from erythrocytes. Studies in a system with flowing human blood.

BACKGROUND: We have explored how hypoxic conditions may affect the antiplatelet effects of aspirin. MATERIALS AND METHODS: For this purpose, a perfusion system containing a damaged vessel segment was modified in order to induce hypoxia (low Po2) in flowing blood. Blood samples were incubated with 50 mumol L-1 aspirin and divided into two aliquots, one being perfused under standard conditions (normoxic) and the other under hypoxic conditions. The interaction of platelets with the subendothelium was morphometrically evaluated. RESULTS: In studies with untreated blood under normoxic conditions, platelet interaction with the subendothelium was 0.3 +/- 0.1% of contact, 5.3 +/- 1.6% of adhesion, 24.3 +/- 3.3% of thrombus and 29.9 +/- 2.7% of total covered surface. Aspirin-treated blood perfused under normoxic conditions showed a marked decrease in thrombus with a concomitant increase in both platelet adhesion and covered surface percentages. However, when aspirin-treated blood was perfused under hypoxic conditions, platelet interaction was not significantly different from that observed in untreated blood. Hypoxia induced a 10-fold increase in ATP release from erythrocytes in the perfusates. If apyrase was added to the perfusates, ATP release was prevented and aspirin effects were evident again. CONCLUSION: Our results suggest that, under hypoxic conditions, the presence of aspirin would not help to inhibit further platelet activation.

Adenosine Triphosphate↗

PubMed1999

Platelet concentrates prepared and stored under currently optimal conditions: minor impact on platelet adhesive and cohesive functions after storage.

BACKGROUND: The effect on platelets of two standard methods of platelet concentrate (PC) preparation was studied by flow cytometry. The findings were correlated with those obtained in an experimental in vitro perfusion model. STUDY DESIGN AND METHODS: PCs were prepared from whole blood by the platelet-rich plasma (PRP) or buffy coat (BC) method and placed on a flatbed platelet agitator at 22 degrees C for up to 5 days. Platelet glycoproteins (GP)lbalpha, GPIIb/IIIa, and GPIV, p-selectin and lysosomal integral membrane protein, and the binding of von Willebrand factor, fibrinogen, fibronectin, and coagulation factor Va were measured with the corresponding specific conjugated antibodies. Perfusions were carried out in an annular chamber with citrated blood depleted of platelets and white cells by filtration, to which samples from PCs were added. RESULTS: PRP-PC production provoked intense platelet activation. In contrast, in BC-derived PCs, platelet activation was milder, and only a significant increase in bound fibrinogen was seen. After 1 day of storage, differences between the methods that had been observed immediately after separation had almost disappeared. During the remaining storage period, increases in activation-dependent antigens and in procoagulant activity were measured. Of the studied platelet GPs, only GPIIIb/ IIIa decreased by 25 percent in PRP-PCs. Differences in covered surface were not significant in perfusion studies performed on Day 0 and after 5 days of storage in PRP-PCs (26.8 +/- 6.9 vs. 20.5 +/- 5.8) or BC-PCs (23.8 +/- 11 vs. 24.8 +/- 10.2). CONCLUSION: Platelet activation occurred during the separation and storage of PCs prepared by both methods, and it was higher in PRP-PCs only in samples obtained immediately after preparation. Despite these changes, platelet adhesive and cohesive functions were similar in both types of PCs and remained basically unchanged after storage.

Blood Platelets↗