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Y Cadroy

Publications and source records attributed to Y Cadroy.

At least 37 records · Page 2Linked to original sources
PubMed1995

Relationship between endothelial tissue factor and thrombogenesis under blood flow conditions.

We have evaluated the relationship between the level of tissue factor (TF) expression by stimulated endothelial cells and thrombus formation under blood flow conditions. Cultures of human umbilical venous endothelial cells (HUVECs) were treated in order to express different levels of TF activity. They were stimulated for 4 h with either I) lipopolysaccharides (LPS, 10 micrograms/ml), II) recombinant interleukin 1 beta (IL1 beta, 50 UI/ml) or III) simultaneously with LPS and IL1 beta (LPS+IL1 beta). TF activity was low on confluent HUVECs or on the corresponding extracellular-matrix (ECM prepared by exposure of HUVECs to 0.1 N NH4OH). In contrast, it was high when HUVECs were stimulated with LPS or IL1 beta, and significantly higher (p < 0.05) with LPS+IL1 beta. The TF activity associated with the stimulated ECM was 2-fold higher (p < 0.05) than that expressed on the luminal surface of the stimulated HUVECs, irrespective of the agonist or combination of agonists used. These surfaces were exposed to non-anticoagulated human blood at a venous (50 s-1) and an arterial (650 s-1) wall shear rate in parallel-plate perfusion chambers for 5 min. Thrombus formation was morphologically quantified by measuring the deposition of platelets and fibrin. Fibrin deposition was also immunologically quantified. Fibrin deposition was related to the level of TF expression. Non-stimulated HUVECs and corresponding ECMs were not thrombogenic. The luminal surface of HUVECs stimulated with LPS or IL1 beta alone expressed low levels of TF activity and was a poor inducer of platelet deposition and fibrin deposition (< 15%) at 50 s-1.(ABSTRACT TRUNCATED AT 250 WORDS)

Antithrombin III↗
PubMed1995

A comparative study of the anticoagulant and anti-thrombotic effects of unfractionated heparin and a low molecular weight heparin (Fraxiparine) in an experimental model of human venous thrombosis.

We have compared the anticoagulant and the antithrombotic effects of unfractionated heparin (Calciparine) and low molecular weight heparin (Fraxiparine) in an experimental human venous thrombosis model. One single subcutaneous injection of Calciparine or Fraxiparine was administered to healthy male volunteers at one month interval in a randomised and cross-over design. Ten subjects received doses used in man for preventing venous thrombosis (5,000 IU and 3,075 IU, respectively), and seven other subjects received curative doses (12,500 IU and 6,150 IU, respectively). Thrombus formation was measured 3 h and 8 h after drug administration. Non-anticoagulated human blood was drawn for 5 min directly from an antecubital vein over confluent cultured endothelial cells positioned in a parallel-plate perfusion chamber. The cells were previously stimulated for 4 h with lipopolysaccharides (10 micrograms/ml) and interleukin 1 beta (50 U/ml), resulting in optimal expression of biological active tissue factor. The wall shear rate at the cell surface was 50 s-1 and mimicked venous blood flow conditions. Immunologically quantified fibrin deposition on the stimulated cells was reduced only by curative doses of Calciparine and Fraxiparine at 3 h (3.4 +/- 0.8 versus 1.0 +/- 0.2 micrograms/cm/ and 2.6 +/- 0.8 versus 1.0 +/- 0.1 micrograms/cm2, respectively, p < or = 0.05). The influence of Calciparine and Fraxiparine on the formation of thrombin and fibrin was determined by measuring the plasma levels of thrombin-antithrombin III complexes and fibrinopeptide A (FPA) in blood samples collected distally to the perfusion chamber. The generation of these markers was significantly inhibited (50-83%) by both prophylactic and curative doses of Calciparine and Fraxiparine (p < or = 0.05). However, Fraxiparine still significantly inhibited the thrombin and fibrin generation at 8 h (p < or = 0.05), whereas Calciparine did not. The antithrombotic effects of both heparins were correlated with their plasma activities as measured by the antifactor Xa or the antithrombin assays. Thus, it appears in this model that Calciparine and Fraxiparine produce comparable antithrombotic effects at clinically comparable doses. However Fraxiparine has a longer-lasting anticoagulant activity than Calciparine. These results are in good agreement with clinical observations in man, and thus in favour of our model of human venous thrombogenesis for further studies of antithrombotic molecules.

Adolescent↗
PubMed1994

Effect of blood flow on thrombin generation is dependent on the nature of the thrombogenic surface.

We have investigated the influence of blood flow on thrombin generation, fibrin formation, and fibrin deposition on procoagulant and nonprocoagulant surfaces. Nonanticoagulated human blood was drawn for 5 minutes directly from an antecubital vein over stimulated endothelial cells expressing tissue factor and over human type III collagen fibrils, positioned in parallel-plate perfusion chambers. The shear rates at these surfaces were 50, 650, and 2,600 s-1. Deposition of platelets and fibrin was measured by morphometry. Thrombin and fibrin formation was determined by measuring prothrombin fragments 1 + 2 (F 1 + 2), thrombin-antithrombin III complexes, (T-AT) and fibrinopeptide A (FPA) in blood effluent from the perfusion chamber at the end of the 5-minute perfusion period. On procoagulant endothelial cells, the thrombi were primarily composed of fibrin. The fibrin deposition (81%, 21%, and 2% at 50, 650, and 2,600 s-1, respectively) and plasma levels of F 1 + 2, T-AT and FPA were shear rate dependent and highest at 50 s-1. There was a positive correlation between F 1 + 2 and T-AT and the fibrin deposition (P < .01). In contrast, the collagen surface triggered primarily thrombi that were composed of platelets. The platelet thrombi and plasma levels of F 1 + 2 and T-AT were also dependent on the shear rate, but highest at 650 and 2,600 s-1. F 1 + 2 and T-AT reached the same level as observed with procoagulant endothelial cells at the higher shear rates. There was a positive correlation between F 1 + 2 and T-AT and the platelet thrombus formation (P < .05), confirming the predominant role of platelets in thrombin generation. Thus, thrombin formation is strongly influenced by the blood flow, and this effect depends on the composition of the thrombogenic surface.

Antithrombins↗
PubMed1994

Relative antithrombotic effects of monoclonal antibodies targeting different platelet glycoprotein-adhesive molecule interactions in nonhuman primates.

The relative antithrombotic effectiveness of targeting glycoprotein (GP) Ib-dependent versus GPIIb-IIIa-dependent platelet interactions has been determined in baboons by measuring thrombus formation after infusing comparable antihemostatic doses of anti-von Willebrand factor (vWF) monoclonal antibody (MoAb) BB3-BD5, anti-GPIb MoAb AP1, and anti-GPIIb-IIIa MoAb LJ-CP8 under conditions of arterial and venous flow (shear rates of 750 to 1,000 seconds-1 and 100 seconds-1, respectively). Thrombus formation was quantified as 111In-platelet deposition and 125I-fibrin accumulation on segments of collagen-coated tubing interposed in chronic exteriorized arteriovenous (AV) shunts for 40 minutes. In vitro, anti-vWF MoAb BB3 BD5 (IgG) and anti-GPIb MoAb AP1 [IgG or F(ab)2 fragments] inhibited ristocetin-induced platelet aggregation (IC50 50 nmol/L and 1 mumol/L, respectively), but neither of these MoAbs blocked platelet aggregation induced by adenosine diphosphate (ADP) (P > .5). Conversely, anti-GPIIb-IIIa MoAb LJ-CP8 inhibited platelet aggregation induced by ADP (IC50 1 mumol/L, but failed to block ristocetin-induced platelet aggregation (P > .5). In vivo, the intravenous infusion of anti-vWF MoAb BB3 BD5 or anti-GPIIb-IIIa MoAb LJ-CP8 into baboons at doses that abolished corresponding agonist-induced aggregation ex vivo (bolus injections of 0.5 mg/kg and 10 mg/kg, respectively) prolonged template bleeding times from baseline values of 4.0 +/- 0.3 minutes to > 27 +/- 4 minutes, and to > 26 +/- 4 minutes, respectively (P < .001 in both cases), without affecting the peripheral platelet count (P > .5). However, injection of anti-GPIb MoAb AP1 [10 mg/kg as IgG or 1 mg/kg as F(ab)2 fragments] produced immediate irreversible thrombocytopenia (< 40,000 platelets/microL). Anti-GPIIb-IIIa MoAb LJ-CP8 abolished platelet deposition and fibrin accumulation on collagen segments under both arterial and venous flow conditions (P < .01 in all cases), whereas MoAb BB3 BD5 produced minimal inhibition of platelet deposition and no decrease in fibrin accumulation at arterial shear rates and undetectable antithrombotic outcomes at low shear. Thus, inhibiting GPIIb-IIIa-dependent platelet recruitment abrogates both thrombus formation and platelet hemostatic function at both venous and arterial shear rates. By contrast, interfering with GPIb-vWF-dependent platelet interactions abolishes platelet hemostatic function without producing corresponding antithrombotic effects.

Animals↗
PubMed1993

Antithrombotic effects of synthetic pentasaccharide with high affinity for plasma antithrombin III in non-human primates.

The pentasaccharide (PS) comprising the minimal heparin structure capable of binding with antithrombin III (ATIII) and exhibiting anti-factor Xa (anti-fXa) activity in plasma without producing detectable antithrombin activity, has been evaluated for its relative antithrombotic and antihemostatic effects in a baboon model combining both platelet-rich and fibrin-rich thrombosis. Thrombosis was produced in a two-component thrombogenic device incorporated into an exteriorized femoral arteriovenous (AV) shunt in baboons; the proximal component constituted a segment of collagen-coated tubing and induced platelet-rich arterial-type thrombus, while the distal component consisted of an expanded chamber producing static and disturbed flow and initiated fibrin-rich venous-type thrombosis. Thrombus formation was measured as the deposition of 111In-platelets and the accumulation of 125I-fibrin. PS was administered intravenously to maintain plasma anti-fXa activity at three different levels: a) low dose (LD) 0.3 +/- 0.1 U/ml; b) intermediate dose (ID) 0.6 +/- 0.1 U/ml; and c) high dose (HD) 5.6 +/- 0.4 U/ml. In untreated controls, thrombus formed rapidly, reaching a plateau by 40 min of 2.3 +/- 0.2 x 10(9) platelets and 0.62 +/- 0.04 mg fibrin deposited on the collagen segments, and 1.9 +/- 0.4 x 10(9) platelets and 3.3 +/- 0.4 mg fibrin accumulated in the chambers.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Evaluation of six markers of haemostatic system in normal pregnancy and pregnancy complicated by hypertension or pre-eclampsia.

OBJECTIVE: To establish the plasma evolution of prothrombin fragments 1+2 (F 1+2), thrombin-antithrombin III complexes (TAT), fibrin fragment D-Dimers (DD), von Willebrand factor antigen (vWf), Type 1 plasminogen activator inhibitor antigen (PAI) and blood platelet count during normal pregnancy and to compare these values with those obtained in hypertensive or pre-eclamptic pregnancies. DESIGN: Cross-sectional study. SUBJECTS: Forty-seven healthy pregnant women with gestational age ranging between 5 and 40 weeks, and fourteen women with gestational age ranging between 25 and 38 weeks presenting with either gestational hypertension (n = 4) or pre-eclampsia (n = 10). Numbers of nulliparous women in the control, hypertension and pre-eclampsia groups were 13/47 (28%), 1/4 (25%) and 9/10 (90%), respectively. RESULTS: All six markers increased with gestational age in normal pregnant women (P < 0.01). Using the upper limit of 95% prediction interval obtained from regression curves as normality threshold, TAT showed the best sensitivity (71% vs < 30% for F1+2, DD, vWf, PAI and platelet count). CONCLUSION: TAT appears to be an interesting marker for detecting haemostatic system alterations in pregnancies complicated by hypertension or pre-eclampsia. A large prospective study to determine its clinical usefulness for such complicated pregnancies is currently in progress.

Adult↗
PubMed1993

Human type II hyperlipoproteinemia enhances platelet-collagen adhesion in flowing nonanticoagulated blood.

We investigated the effects of high plasma lipid levels on platelet adhesion and platelet thrombus formation in nonanticoagulated human blood on collagen fibrils at an arterial wall shear rate of 2600 seconds-1. Nonanticoagulated blood was drawn directly at a flow rate of 10 mL/min for 3 minutes from an antecubital vein of patients with type IIa (n = 5) and type IIb (n = 4) hyperlipoproteinemia over purified human type III collagen fibrils that were positioned on a plastic coverslip in a parallel-plate perfusion chamber. Results were compared with those obtained in healthy individuals with normal lipid plasma levels (n = 9). Blood-collagen interactions were quantified by morphometry as platelet-collagen adhesion, thrombus volume, and fibrin deposition. Platelet-collagen adhesion in the two groups of patients was significantly higher than in healthy individuals (70.7 [61.2 to 82.0] and 70.3 [66.4 to 81.0] in types IIa and IIb patients, respectively, versus 51.2 [44.5 to 68.6] in control subjects; P < .05. All values are percent median [range]). In contrast, the thrombus volume was similar in the three groups (11.3 [8.0 to 13.0], 9.6 [6.4 to 15.3], and 10.2 [6.8 to 16.1] microns3/microns2 [range], respectively). Differences in fibrin deposition were not observed. Thus, it appears that platelet-collagen adhesion is augmented in patients with type IIa and IIb hyperlipoproteinemia, indicating that the process of thrombogenesis is hastened in these patients.

Adult↗
PubMed1993

Dermatan sulfate inhibition of fibrin-rich thrombus formation in nonhuman primates.

Dermatan sulfate (DS), a factor that amplifies plasma heparin cofactor II antithrombin (HCII) activity, has been evaluated in baboons for its relative antithrombotic and antihemostatic effects by use of a model that combines both platelet-rich and fibrin-rich thrombus formation. Thrombus was generated in a two-component thrombogenic device incorporated into exteriorized femoral arteriovenous shunts, in which a proximal segment of collagen-coated tubing induces platelet-rich arterial-type thrombus and distal expanded chambers with disturbed and static flow produce fibrin-rich venous-type thrombus. Thrombus formation was measured as the deposition of autologous 111In-platelets by imaging analysis and by the accumulation of 125I-fibrin. Intravenous infusion of DS at 0.83, 8.3, and 42 mg/kg maintained plasma levels at approximately 7, 70, and 400 micrograms/mL, respectively, throughout the period of study. By enhancing HCII-dependent inactivation of soluble thrombin, DS prolonged the coagulation times, reduced plasma fibrinopeptide A levels, and decreased fibrin-rich thrombus formation in the chamber portion of the device in a dose-dependent manner, ie, the intermediate dose reduced fibrin accumulation by approximately 70% (P < .05). By contrast, neither platelet deposition on collagen nor platelet hemostatic function, assessed with bleeding time determinations, was significantly affected by DS at any dose studied (P > .2 and P > .1, respectively, for the high dose), a finding presumably explained by the resistance of immobilized thrombin to inactivation by DS.

Animals↗
PubMed1992

Influence of aging on the activity of the hemostatic system: prothrombin fragment 1+2, thrombin-antithrombin III complexes and D-dimers in 80 healthy subjects with age ranging from 20 to 94 years.

To determine the influence of aging on the activity of the hemostatic system, we measured the plasma concentration of prothrombin fragments 1+2 (F 1+2), thrombin-antithrombin III complexes (TAT) and fibrin degradation fragments D-dimers (D-D) in 80 healthy subjects with age ranging between 20 and 94 years. All subjects were free of acute or chronic diseases. The three markers (semi-log scale) were positively correlated with age (r greater than 0.7, p less than 0.01). Mean plasma levels of F 1+2, TAT and D-D were two- to five-fold higher in subjects with age greater than or equal to 60 as compared to those less than 60 years (n = 40 in both groups). In these two groups, normal values for F 1+2, TAT and D-D ranged from 0.3-1.2 vs 0.7-2.4 nmol/l, 1.4-2.6 vs 1.9-6.4 micrograms/l and 33-433 vs 312-1180 micrograms/l, respectively. Sex did not influence the results. We conclude that the activity of the hemostatic system is markedly age-dependent, and that elderly subjects display a biological picture of "prethrombotic" state. In addition, for a right clinical use of these three markers, age should be taken into account when normal range is to be established.

Adult↗
PubMed1992

Antihemostatic and antithrombotic effects of monoclonal antibodies against von Willebrand factor in nonhuman primates.

BACKGROUND: Because the adhesive glycoprotein von Willebrand Factor (vWF) mediates initial platelet attachment at sites of vascular injury and may also contribute to shear-dependent platelet thrombus formation, we have determined in vivo the relative antithrombotic efficacy and hemostatic safety of infusing murine monoclonal antibodies against vWF. METHODS: In baboons with chronic arteriovenous shunts, thrombus formation was initiated by interposition of thrombogenic Dacron vascular grafts (VG) and endarterectomized baboon aortic segments (EAS). Thrombus formation on VG and EAS was assessed by use of real-time scintillation camera imaging of indium 111-labeled platelet deposition. In control and treated animals (anti-vWF antibody) platelet hemostatic competence was evaluated by means of serial measurements of platelet count, bleeding time, and ex vivo platelet aggregation in response to adenosine diphosphate and ristocetin. RESULTS: Although bolus antibody infusions did not affect circulating platelet counts, bleeding times were immediately prolonged to 28 +/- 4 minutes (vs 4.7 +/- 0.4 minutes before treatment, p = 0.01). Bleeding times normalized within 24 hours after antibody administration. Platelet aggregation in response to adenosine diphosphate was unchanged by antibody therapy, whereas ristocetin-induced platelet aggregation was abolished acutely and remained impaired for 24 hours. Platelet deposition on VG after 60 minutes of exposure to flowing blood was 2.95 +/- 0.74 x 10(9) platelets/cm in six control animals as compared to 1.86 +/- 0.16 x 10(9) platelets/cm in five treated animals (p = 0.04). Similarly, platelet deposition on EAS averaged 4.40 +/- 0.89 x 10(9) platelets/cm in control studies and was reduced significantly by antibody therapy (1.52 +/- 0.50 x 10(9) platelets/cm, p = 0.02). CONCLUSIONS: Despite profound interruption of platelet hemostatic functions, therapeutic targeting of vWF modestly inhibits platelet-dependent thrombosis.

Animals↗
PubMed1991

Hirudin interruption of heparin-resistant arterial thrombus formation in baboons.

To determine the role of thrombin in high blood flow, platelet-dependent thrombotic and hemostatic processes we measured the relative antithrombotic and antihemostatic effects in baboons of hirudin, a highly potent and specific antithrombin, and compared the effects of heparin, an antithrombin III-dependent inhibitor of thrombin. Thrombus formation was determined in vivo using three relevant models (homologous endarterectomized aorta, collagen-coated tubing, and Dacron vascular graft) by measuring: (1) platelet deposition, using gamma camera imaging of 111In-platelets; (2) fibrin deposition, as assessed by the incorporation of circulating 125I-fibrinogen; and (3) occlusion. The continuous intravenous infusion of 1, 5, and 20 nmol/kg per minute of recombinant hirudin (desulfatohirudin) maintained constant plasma levels of 0.16 +/- 0.03, 0.79 +/- 0.44, and 3.3 +/- 0.77 mumol/mL, respectively. Hirudin interrupted platelet and fibrin deposition in a dose-dependent manner that was profound at the highest dose for all three thrombogenic surfaces and significant at the lowest dose for thrombus formation on endarterectomized aorta. Thrombotic occlusion was prevented by all doses studied. In contrast, heparin did not inhibit either platelet or fibrin deposition when administered at a dose that maximally prolonged clotting times (100 U/kg) (P greater than .1), and only intermediate effects were produced at 10-fold that dose (1,000 U/kg). Moreover, heparin did not prevent occlusion of the test segments. Hirudin inhibited platelet hemostatic function in concert with its antithrombotic effects (bleeding times were prolonged by the intermediate and higher doses). By comparison, intravenous heparin failed to affect the bleeding time at the 100 U/kg dose (P greater than .5), and only minimally prolonged the bleeding time at the 1,000 U/kg dose (P less than .05). We conclude that platelet-dependent thrombotic and hemostatic processes are thrombin-mediated and that the biologic antithrombin hirudin produces a potent, dose-dependent inhibition of arterial thrombus formation that greatly exceeds the minimal antithrombotic effects produced by heparin.

Animals↗
PubMed1991

Selective inhibition by a synthetic hirudin peptide of fibrin-dependent thrombosis in baboons.

To determine the importance of the thrombin substrate recognition exosite for fibrinogen binding in the formation of both arterial and venous thrombi, we evaluated the antithrombotic effects of the tyrosine-sulfated dodecapeptide from residues 53-64 of hirudin (H peptide) in a nonhuman primate model. This peptide was studied because it inhibits thrombin cleavages of fibrinogen by simple competition without blocking enzyme catalytic-site function. When an exteriorized arteriovenous access shunt model was used in baboons (Papio anubis), thrombus formation was induced by placing a thrombogenic device made of (i) a segment of tubing coated covalently with type I collagen, which generated platelet-rich thrombi under arterial flow conditions, and (ii) two subsequent annular regions of flow expansion that produced fibrin-rich thrombi typically associated with venous valves and veins. Thrombus formation was quantified by measurements of 111In-labeled platelet and 125I-labeled fibrinogen deposition in both arterial-flow and venous-flow portions of the device. Continuous infusion of H peptide (0.5, 15, and 75 mg/kg) proximal to the device for 40 min interrupted, in a dose-response fashion, formation of fibrin-rich thrombus in the regions of disturbed flow and generation of fibrinopeptide A. In contrast, H peptide did not inhibit the capacity of platelets to deposit on the collagen surface (P greater than 0.2 at all doses) or to form hemostatic plugs (as assessed by measurements of bleeding time; P greater than 0.1 at all doses). These findings suggest that, by competitive inhibition of fibrinogen binding to thrombin, fibrin-rich venous-type thrombus formation may be selectively prevented. This strategy may be therapeutically attractive for preserving normal platelet function when conventional anticoagulant therapy is contraindicated.

Animals↗
PubMed1990

Effects of red blood cell concentration on hemostasis and thrombus formation in a primate model.

Because the effects of red blood cell (RBC) concentration on hemostasis and thrombus formation have not been studied experimentally under conditions of whole blood flow without anti-coagulation, normal baboons were bled or transfused to obtain three different groups: a low hematocrit (Ht) group (20% less than Ht less than 25%), a normal Ht group (35% less than Ht less than 40%), and a high Ht group (50% less than Ht less than 55%). Measurements of platelet count, bleeding time, platelet aggregation, fibrinogen level, and coagulation time (APTT) were equivalent to normal values in each group. Thrombus formation was induced using a device composed of collagen-coated tubing followed by two sequentially placed expansion chambers designed to exhibit flow recirculation and stasis. The device was exposed for up to 40 minutes in an arterio-venous shunt system. Wall shear rates in the tubular collagen segment were 100 seconds-1 and 500 to 750 seconds-1. The accumulation of 111In-platelets and 125I-fibrinogen/fibrin was measured radioisotopically; RBC incorporation was determined from measurements of total thrombus hemoglobin. Thrombus that formed on the collagen substrate was rich in platelets and poor in fibrin and RBCs. Under high flow conditions, thrombus composition showed no dependence on Ht. Surprisingly, under low flow conditions, platelet thrombus volume was negatively correlated with Ht (r = -.73, P = .005), and was increased by greater than twofold in the low Ht group as compared with the high Ht group. Thrombus that formed in the disturbed flow regions contained relatively few platelets but was rich in fibrin and RBCs. The predominant finding was a positive correlation between RBC incorporation and Ht at both high and low shear rates (r = .90, P = .00003; and r = .77, P = .002, respectively), with thrombus volume increasing three- to sixfold between the low and high Ht groups. Thus, in vivo variations in Ht ranging between 20% and 55% did not affect hemostasis, but were found either to promote or inhibit the net accumulation of thrombus, depending on local flow conditions.

Animals↗