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Biomedical subjects

L Drouet

Publications and source records attributed to L Drouet.

At least 19 recordsLinked to original sources
PubMed1996

An experimental model for testing von Willebrand factor function: successful SLA-matched crossed bone marrow transplantations between normal and von Willebrand pigs.

To assess the relative in vivo roles of von Willebrand factor (vWF) of different origins, we performed crossed bone marrow transplantations (BMTs) among normal pigs and pigs with the von Willebrand disease(vWF). The two groups were fully compatible immunologically according to typing by swine leukocyte antigen (SLA). After total-body irradiation (8-10 Gy), all pigs received 0.5X10(9) to 10(10)/kg mononuclear bone marrow cells without any immunosuppression. The nadir of aplasia occurred between days 5 and 7 after irradiation (white blood cell [WBC] count 0.6X10(9)/L, platelet [Plt] count 76X10(9)/L. Three weeks after the graft, WBC and Plt counts had returned to normal levels. Animals were followed for at lease 50 days, during which no bone marrow rejection occurred; no evidence of graft-vs-host disease (GVHD) was observed. Each BMT was confirmed by karyotype analysis. In the six homozygous pigs with vWD grafted with normal marrow, platelet vWF antigen (vWFAg) and platelet vWF activity rose from <3 to 450 U/dl with a normal multimeric pattern; plasma vF increases slightly. No correction of bleeding time was observed. In the five normal pigs grafted with bone marrow form pigs with vWD, platelet vWFAg and platelet vWF activity decreased from >100 U/dl to undetectable levels; bleeding time and plasma vWFAg remained unchanged. A derivative of normal porcine plasma, a concentrate containing factor VIII and vWF, was infused into a homozygous vWD pig before and after BMT from a normal pig. Co correction of bleeding time was obtained, even though plasma nd platelet vWFAg levels were normal. W concluded that crossed BMT among SLA-identical pigs is a feasible model of studying the synthesis and the roles of vWF in hemostasis and thrombosis.

Animals↗
PubMed1995

Autologous platelet concentrate for the treatment of full-thickness macular holes.

BACKGROUND: To improve the anatomic success rate in the surgery of full-thickness macular holes, we tested, in a prospective pilot study, the effects of autologous platelet concentrate deposited on the macula at the end of surgery. METHODS: Two consecutive groups of patients were compared. Twenty eyes (group 1, mean symptom duration 11 months) were operated on with injection of an autologous platelet concentrate on the macula after fluid-gas exchange. Another 20 eyes (group 2, mean symptom duration 11 months) were subsequently operated on without autologous platelet concentrate. For all stage 3 holes, posterior hyaloid was detached en bloc at the level of the optic disc. The patient was left supine for 24 h after surgery, and then remained face down for 10 days. RESULTS: In group 1, 19 cases were an anatomic success, i.e. there was flattening of the retina surrounding the hole and reattachment of the edge of the hole to the retinal pigment epithelium; in 9 cases the hole was even undetectable. Final visual acuity was 0.5 or more in 9 eyes, and 0.4 or more in 14. Visual acuity improved by two lines or more in 17 of the 19 successfully operated eyes. In group 2, only 13 cases were an anatomic success. The functional results for the successfully operated eyes were identical to those of group 1. CONCLUSION: These results strongly suggested that autologous platelet concentrate could significantly improve the success rate in macular hole surgery and led us to begin a comparative, prospective, randomized trial.

Adult↗
PubMed1995

Increased plasma serotonin in primary pulmonary hypertension.

PURPOSE: Pulmonary hypertension can occur in patients who have disorders associated with altered platelet serotonin storage, including collagen vascular disease and platelet storage pool disease. We tested the hypothesis that primary pulmonary hypertension (PPH) may be also associated with impaired handling of serotonin by platelets, resulting in increased plasma serotonin levels. PATIENTS AND METHODS: We used radioenzymatic assays to measure serotonin in platelets and plasma and serotonin released during in vitro platelet aggregation in 16 patients with PPH, and in 16 normal controls matched for age and sex. Six patients were restudied after heart-lung transplantation to determine whether serotonin abnormalities persisted after pulmonary arterial pressure returned to normal. RESULTS: Patients had decreased platelet serotonin concentration (1.8 +/- 0.6 x 10(-18) mol/platelet versus 3.2 +/- 0.2 x 10(-18) mol/platelet in controls; P < 0.01) and increased plasma serotonin concentration (30.1 +/- 9.2 x 10(-9) mol/L versus 0.6 +/- 0.1 x 10(-9) mol/L in controls; P < 0.001). Serotonin released during in vitro platelet aggregation was higher in patients than in controls. After heart-lung transplantation, platelet serotonin concentrations remained decreased and plasma levels remained increased. CONCLUSIONS: Abnormal handling of serotonin by platelets leading to an increase in plasma serotonin occurs in PPH. The persistent decrease in platelet storage of serotonin after heart-lung transplantation suggests that this platelet abnormality is not secondary to PPH.

Adult↗
PubMed1995

[Comparison of the effects of ketorolac and aspirin on hemostasis in the rabbit].

OBJECTIVE: Comparison of ketorolac with aspirin and placebo for the antithrombotic activity using the Folts' model of experimental arterial thrombosis and the perioperative blood loss. STUDY DESIGN: Experimental randomized blinded study anaesthetized, tracheotomized and mechanically ventilated. Carotid blood flow variations were detected by a probe directly inserted around the artery and monitored by an electromagnetic flowmeter. A segment of the exposed carotid artery was de-endothelialized by gently squeezing the artery with a needle holder forceps, and an external constrictor was placed around it (stenosis 60%), to induce cyclic flow reductions (CFR). During 20 min, CFR rate was assessed. Animals were then randomized in 3 groups of 9: ketorolac (K) 1 mg.kg-1, aspirin (A) 10 mg.kg-1 or saline (S), injected intravenously (peripheral ear vein). After drug administration, CFR rate was assessed over 20 min, to determine the potential antithrombotic activity of the drug (curative phase). Thereafter, the opposite carotid artery was injured and stenosed and the occurrence of CFR was assessed over 20 min (preventive phase). The amount of blood loss of a xipho-pubic laparotomy with a spleen section was also measured 30 min after drug administration. RESULTS: In all untreated animals, CFRs developed with a mean rate of 4 cycles/20 min. Aspirin completely abolished CFR during the curative phase in all rabbits, except in one. No effect was observed during this phase with ketorolac or saline. During the preventive phase, a partial inhibition of CFRs was induced by ketorolac and aspirin. Peri-operative bleeding was not increased significantly by ketorolac or aspirin. Postinjection bleeding-time did not differ between the three groups. CONCLUSIONS: Ketorolac (1mg.kg-1) has not a strong antithrombotic activity. Ketorolac and aspirin do not increase peri-operative blood loss, and therefore do not seem to strongly interfere with haemostasis in the rabbit.

Animals↗
PubMed1995

Characterization of an antithrombotic peptide from kappa-casein in newborn plasma after milk ingestion.

Bovine and human kappa-caseinoglycopeptides, two antithrombotic peptides derived from the corresponding kappa-caseins, were detected in physiologically active concentrations in the plasma of 5-d-old newborn infants after ingestion of cow's-milk-based formula or human milk respectively. It is suggested that these two bioactive peptides are released from milk proteins during digestion.

Amino Acid Sequence↗
PubMed1995

Cross-reactivity of human molecular markers for detection of prethrombotic states in various animal species.

The aim of the present study was to investigate the reactivity of immunoreagents developed for clinical applications in humans in different animal species (hen, mouse, rat, rabbit, guinea-pig, dog, pig, sheep, baboon). Prothrombin fragment 1 + 2, thrombin-antithrombin III complex and fibrinopeptide A were tested for coagulation, platelet factor 4 and beta-thromboglobulin for platelet activation, glycoprotein IIb-IIIa, glycoprotein Ib and P-selectin for platelet membrane glycoproteins, D-dimers for fibrinolysis, thrombomodulin for activation of endothelial cells and thrombospondin and von Willebrand factor for adhesive proteins. Prothrombin fragment 1 + 2, platelet factor 4, beta-thromboglobulin and D-dimers were revealed only in baboons. Fibrinopeptide A was well detected in baboons but weakly in mice, dogs, pigs and sheep. Whereas glycoprotein IIb-IIIa was revealed on guinea-pig, dog and sheep platelets and glycoprotein Ib on rabbit and dog platelets, P-selectin and thrombomodulin were never detected. Thrombospondin was revealed in hens, mice, rats, guinea-pigs, pigs, sheep and baboons and von Willebrand factor in mice, rats, guinea-pigs, dogs, pigs, sheep and baboons. Interestingly, thrombin-antithrombin III complex (TAT) was detected in all species tested except the hen. A time- and dose-dependent increase in TAT was observed when rats, dogs or pigs were infused with thromboplastin (4.5-450 microliters/kg/h), while administration of hirudin (1 mg/kg) abolished this TAT generation. Thus, the TAT immunoassay could provide a tool for the screening of antithrombotic drugs in a number of animal species. However, the possibility of using a wider panel of human immunoreagents would appear to be restricted to baboons which display good species cross-reactivity.

Animals↗
PubMed1995

Absence of incorporation of plasma von Willebrand factor into porcine platelet alpha-granules.

In order to study the relationship between plasma and platelet von Willebrand factor (vWF), we used an experimental model of crossed bone marrow transplantation (BMT) between SLA immunocompatible normal and homozygous von Willebrand (vWD) pigs. A normal pig received bone marrow from a vWD pig and a second pig with vWD was engrafted with marrow from a normal pig. Each recipient, after total irradiation of 10 Grays, received by a central catheter 10(10) monocellular bone marrow cells without immunosuppression. The animals were followed for 50 d and no graft rejection or graft-versus-host disease was observed. After aplasia occurring 3 weeks after BMT, white blood cells and platelets returned to normal. Before transplantation, in the vWD pig, vWFAg and vWF activity were not detected in plasma and in platelet and megakaryocyte alpha-granules. After transplantation with normal marrow, platelet vWFAg and platelet vWF activity wer normal and high molecular weight multimers and numerous tubular structures were present in alpha-granules. Before transplantation, the normal pig had normal plasma and platelet vWFAg-vWF activity, normal multimeric pattern, and the platelet and megakaryocyte alpha-granules displayed many tubular structures, eccentrically located in one of their poles, coinciding with immunogold staining vWFAg. After transplantation with homozygous vWD marrow, platelet and megakaryocyte alpha-granules lacked tubular structures. Alpha-granule immunogold staining for vWF was consistently negative, although plasma vWF was at a normal level. In conclusion, this study shows that, unlike other plasma proteins such as fibrinogen. vWF endocytosis does not occur from plasma to the platelet alpha-granules. Platelet and megakaryocyte vWF solely originates from megakaryocyte endogenous synthesis and is independent of plasma vWF.

Animals↗
PubMed1995

Antithrombotic effect of a recombinant von Willebrand factor, VCL, on nitrogen laser-induced thrombus formation in guinea pig mesenteric arteries.

To assess the antithrombotic effectiveness of blocking the platelet glycoprotein (GP) Ib/IX receptor for von Willebrand factor (vWF), the antiaggregating and antithrombotic effects were studied in guinea pigs using a recombinant fragment of vWF, Leu 504-Lys 728 with a single intrachain disulfide bond linking residues Cys 509-Cys 695. The inhibitory effect of this peptide, named VCL, was tested in vitro on ristocetin- and botrocetin-induced platelet aggregation and compared to the ADP-induced platelet aggregation. In vivo, the antithrombotic effect of VCL was tested in a model of laser-injured mesentery small arteries and correlated to the ex vivo ristocetin-induced platelet aggregation. In this model of laser-induced thrombus formation, five mesenteric arteries were studied in each animal, and the number of recurrent thrombi during 15 min, the time to visualization and time to formation of first thrombus were recorded. In vitro, VCL totally abolished ristocetin- and botrocetin-induced platelet aggregation, but had no effect on ADP-induced platelet aggregation. Ex vivo, VCL (0.5 to 2 mg/kg) administered as a bolus i.v. injection inhibits risocetin-induced platelet aggregation with a duration of action exceeding 1 h. The maximum inhibition was observed 5 min after injection of VCL and was dose related. The same doses of VCL had no significant effect on platelet count and bleeding time.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1994

How does ticlopidine treatment lower plasma fibrinogen?

Many clinical studies have evaluated the clinical efficiency of ticlopidine in vascular pathology and in few of these studies the plasma Fg level was determined as a biological parameter and not a primary end point. All these studies are heterogeneous because plasma Fg concentration have been measured using various methods, patients were included at various time after the acute event and were followed over a period of 1 to 24 months of treatment with ticlopidine, patients suffered from various pathology: peripheral arterial disease, cerebrovascular disease, diabetes or polycythemia vera. Despite the heterogeneity of these prospective studies, a general trend indicates a decrease in the plasma Fg levels by 10 to 25% with ticlopidine compared to placebo. This decrease in circulating Fg was associated with clinical improvement, and, when studied, hemorheological modifications (decreases in whole blood and plasma viscosities). The mechanism of ticlopidine action is discussed.

Blood Viscosity↗
PubMed1994

French multicentric evaluation of recombinant tissue factor (recombiplastin) for determination of prothrombin time.

Recombiplastin, a recombinant a human tissue factor, elaborated by Ortho Diagnostic Systems, produced by Baculovirus and relipidated with highly purified phospholipids, was tested as a new reagent for determining prothrombin time (PT) in a French multicentric study. Its intralaboratory performances, including sensitivity, repeatability, reproducibility and stability, were explored to establish whether its use would reduce the interlaboratory dispersion of PT values, and therefore improve the standardization of oral anticoagulant treatment. The 9 university hospital hematology laboratories involved in this study used the same type of instrument (KC 10). For 10 consecutive days, they determined PTS on a normal plasma pool, plasma dilutions of 1/2, 1/3 and 1/8, 3 identical lyophilized calibrated plasmas, as well as plasmas from 20 normal subjects, 50 patients on oral anticoagulant therapy with Recombiplastin which has an International Sensitivity Index (ISI) of 1, and 2 commercial thromboplastin extracts (ISI #1 or 2). In the patients on anticoagulants, factors VII, X and V were measured when results were conflicting. The intra and interlaboratory reproducibilities of Recombiplastin, calculated on the basis of either PTS expressed in seconds, or of the International Normalized Ratio (INR), were good, with coefficients of variation (CV) similar to those observed with the 5 other reagents used by the different laboratories (2% < CV < 8%). The stability of Recombiplastin was excellent, with no variation in PT after 72 h of incubation at 37 degrees C. A normal PT of 12 s was obtained with Recombiplastin, similar to the values found for the reagents with ISI #2.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1993

[Low molecular weight heparins].

Low molecular weight heparins (LMWH) have been commercially available in France for several years. Their effectiveness and easier use perhaps explain why, among all European and American physicians, the French are the only ones who prefer to prescribe LMWH. In France, the preferential use of LMWH is already common practice for prevention of deep vein thrombosis (DVT) and should reach this position for the treatment of DVT in a near future. But among these practices it is necessary to distinguish those which are established on scientific grounds from those which are accepted, but not established, and those which are still unanswered clinical questions. Among the points established is the use of LMWH to prevent DVT in general and orthopaedic surgery and in medicine, and in the treatment of DVT. Among those which are generally accepted, although not fully established, are the lower haemorrhagic risk/efficiency ratio compared with standard heparin, the absence of need to measure anti Xa in prevention, the lower risk of heparin-induced thrombocytopenia, the effectiveness and absence of specific risk when used during pregnancy. The points which are not yet solved (but are becoming of common practice) are the lack of need to measure anti Xa activity, even when indicated for treatment of established DVT, and the absence of risk of osteoporosis. Among the points which are still debatable questions are the comparative efficacy of administration before or immediately after surgery (a crucial point for the management of patients receiving lumbar anaesthesia). In view of the numerous on-going clinical trials involving LMWH it is necessary to have frequent review, such as this one, to keep abreast of established data.

Female↗
PubMed1993

Biologically active peptides from milk proteins with emphasis on two examples concerning antithrombotic and immunomodulating activities.

The present paper is devoted to the study of short peptides derived from milk proteins with physiological activities. Some of them behaved as opioids, enzyme inhibitors that convert angiotensin I, peptides that enhance calcium absorption, antiaggregating and antithrombotic peptides, and immunomodulating peptides. Some possessed several physiological properties, such as the C-terminal part of bovine alpha s1-casein. A strategic zone, containing immunostimulating and opioid peptides, could be located in cow and human beta-caseins. Few of these peptides or precursor peptides have so far been characterized in vivo in blood or brain after ingestion of milk. If, in the future, some of the active peptides cannot be characterized in vivo, they can all nevertheless be synthesized and used either as food additives or in pharmacology.

Amino Acid Sequence↗
PubMed1993

Changes in protein C, factor VII and endothelial markers after autologous bone marrow transplantation: possible implications in the pathogenesis of veno-occlusive disease.

In a recent prospective study of allogenic bone marrow transplantation we reported that decreases in factor VII and protein C were predictive markers for high risk of veno-occlusive disease (VOD). In order to determine the relative involvement of endothelial and hepatocyte injury in the genesis of VOD, 34 consecutive patients undergoing autologous bone marrow transplantation (BMT) were studied. Conditioning was performed by chemotherapy alone or associated with total body irradiation (TBI). Protein C and factor VII, the endothelial markers Von Willebrand factor (vWF and t-PA, fibrinogen and fibronectin were measured weekly before and after BMT. Protein C and factor VII were within the normal range before BMT, decreased significantly on day 7 to 73 and 64% respectively (p < .01) and then returned to normal values. Fibrinogen increased to 7 g/l (p < .001) on day 7 but then returned to normal levels. Fibronectin was abnormally high (p < .001) before BMT and decreased thereafter, while vWF increased (p < 0.001) for three consecutive weeks. t-PA was low (p < 0.001) before conditioning but increased thereafter. These results demonstrate the presence of endothelial lesions before BMT and acute hepatic and endothelial lesions after conditioning. Although VOD was never observed in our patients, this complication could well arise from preexisting vascular lesions due to previous chemotherapy and/or from acute hepatocytic injury, which could also be of endothelial origin, after conditioning.

Biomarkers↗
PubMed1992

Inhibition effects of KRDS, a peptide derived from lactotransferrin, on platelet function and arterial thrombus formation in dogs.

KRDS (Lys-Arg-Asp-Ser), a tetrapeptide from human lactotransferrin, was tested for its effects in vitro on dog platelet function and in vivo on femoral arterial thrombus formation in dogs. KRDS inhibited ADP (8 microM)-induced platelet aggregation (IC50: 350 microM) and arachidonic acid (2 mM)-induced thromboxane B2 generation (IC50: 175 microM). In addition, the thrombin (0.2 U/ml)-induced serotonin release was inhibited by KRDS (IC50: 525 microM) and the expression of alpha-granule membrane protein (GMP-140) was also inhibited (IC50: 350 microM). The results show that KRDS is an inhibitor for platelet aggregation and secretion to which the inhibition is more potent. Meanwhile, in the experiment of arterial thrombosis in dogs, KRDS (5 microM/kg) and 125I-SZ-51 (a monoclonal antibody against GMP-140) were injected before operation and immediately after the thrombus formation, respectively. In the KRDS group, the weight of removed thrombi was reduced to 50% of that in controls and the radioactivity per mg of labeled thrombi to 33.3% while in blood the radioactivity increased 2 times that in controls at the 4th hour after the injection of 125I-SZ-51. The radioactivity ratio between removed thrombi and blood was only 16% of that in controls. These results indicate that KRDS can inhibit thrombus formation in vivo and is a promising antithrombotic agent.

Amino Acid Sequence↗
PubMed1992

Characterization of a thrombopathy (type delta storage pool disease) affecting a pig colony.

An autosomal recessive thrombopathy in pigs is described and characterized functionally, morphologically and biochemically. The affected pigs have a severe bleeding diathesis and a markedly prolonged bleeding time but normal plasma and platelet von Willebrand factor (vWF) levels. Electron micrographs and fluorescence microscopy with mepacrine reveal reduced numbers of dense granules in platelets as compared to normals. This thrombopathy is a pure delta storage pool disease (SPD), as evidenced: a) biochemically by platelet serotonin content and metabolism and by comparative ATP/ADP content and secretion; b) functionally by reduced aggregability to low concentrations of convulxin and collagen but normal aggregability to other agents and normal synthesis of thromboxane B2. The affection was first discovered in a colony of von Willebrand's disease (vWD) pigs, but is biologically and genetically distinct. It is possible to completely separate the SPD from the vWD, although originally animals could be affected by both vWD and SPD. Normal plasma and platelet alpha granule content of vWF are found in diseased animals. An intermediate disorder is also detected in animals not severely affected, which may represent the heterozygous state.

Acetylserotonin O-Methyltransferase↗
PubMed1991

Liver veno-occlusive disease after bone marrow transplantation changes in coagulation parameters and endothelial markers.

Veno occlusive disease (VOD) is a frequent complication of allogenic bone marrow transplantation (BMT) for which no predictive blood markers are available. 39 patients grafted for severe aplastic anemia (18), and leukemia (21) were prospectively studied. Of the 39 patients, 5 leukemic patients, but no aplastic patients developed VOD. In all the 5 patients with VOD complications we demonstrated a decrease in factor VII and in protein C before the clinical onset of the disease and before any changes in hepatic enzymes were observed. This decrease is the earliest sign of hepatic involvement by the VOD suggesting that the determination of Factor VII and protein C can be used as a prediction test to identify the patients who are at risk of developing VOD after transplantation. In addition, a toxicity of the endothelial cells was suggested by the observed increase in von Willebrand factor and in Serum Angiotensin Converting Enzyme. Signs of endothelial toxicity was more pronounced in leukemic than in aplastic patients.

Biomarkers↗
PubMed1991

Heterogeneous distribution of Weibel-Palade bodies and von Willebrand factor along the porcine vascular tree.

Vessels obtained from different levels of pig vascular tree were examined by transmission electron microscope, with the aim of determining whether or not their endothelial cells contain Weibel-Palade bodies (WPB). As these organelles are known to store the von Willebrand factor (vWF), a two-step immunogold labeling of this protein also was performed. Our results showed for the first time a heterogeneous distribution of WPB along the vascular tree of the normal pig: These structures were absent from the thoracic aorta, rare in the abdominal aorta, present in myocardial capillaries, and numerous in the inferior vena cava and pulmonary artery. Atypical WPB devoid of tubules were seen in all endothelial cells. The ultrastructural labeling of vWF demonstrated its presence only in the WPB, being absent in the subendothelium, and showed the same variation in its distribution along the vascular tree as for its storage organelle. Pigs homozygous for the von Willebrand disease were found to have only the atypical WPB, and do not express the vWF.

Aging↗