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Biomedical subjects

A Casonato

Publications and source records attributed to A Casonato.

At least 37 records · Page 2Linked to original sources
PubMed1997

Impairment of fibrinolytic potential in long-term steroid treatment after heart transplantation.

Thrombotic complications constitute an important risk in transplant recipients, in whom a hypercoagulable state and hypofibrinolysis have been associated with immunosuppressive treatment, especially with cyclosporine. In no case have clotting and fibrinolytic abnormalities been correlated with steroid immunosuppression, even though steroids were always administered. Previous studies found a relationship between hypercorticism and hypofibrinolysis both in Cushing's disease and after renal transplantation. The aim of this investigation was to compare fibrinolytic potential using the venous occlusion test in two similar groups of heart transplant patients treated with or without steroids. Euglobulin lysis time, tissue-type plasminogen activator and plasminogen activator inhibitor-1 (PAI-1) activities, and antigens were determined before and after the venous occlusion test. A reduced fibrinolytic potential (significant prolongation of lysis time) due to a significant increase in PAI-1 activity and antigen levels was found in heart transplant patients treated with steroids, as compared with patients without steroid treatment and control subjects. The prevalence of reduced fibrinolytic potential was 69.2% (18 cases) in the steroid-treated group and 34.8% (8 cases) in the non-steroid-treated group. In every case, the impaired fibrinolytic potential was due to high basal PAI-1 levels. Our results are compatible with the presence of a hypofibrinolytic state secondary to long-term steroid treatment. In heart transplant recipients, steroid-induced hypofibrinolysis may constitute a further risk factor for thrombotic disease.

Adolescent↗
PubMed1997

Abnormal collagen binding activity of 2A von Willebrand factor: evidence that the defect depends only on the lack of large multimers.

It is well established that the large von Willebrand factor (vWf) multimers bind with high affinity to the extracellular matrix. To explore the different roles of intermediate and large vWf multimers, we studied the collagen-binding activity (vWf:CBA) of 2A vWf under nonflowing conditions in relation to the multimer organization of the molecule. Regardless of the anticoagulant used for blood collection, vWf:CBA was significantly decreased, in 4 patients with 2A von Willebrand's disease (vWd), in accordance with the lack of high and intermediate vWf multimers. After 1-deamino-8-D-arginine vasopressin (DDAVP) infusion, the appearance of circulating large and unusually large vWf multimers, in samples collected in the presence of protease inhibitors, induced a complete normalization of vWf:CBA. The peak was observed 15 minutes after DDAVP, when large and unusually large multimers were maximally represented. These effects were transient because vWf:CBA decreased after 60 minutes, even though values were still significantly higher than pre-DDAVP figures; at the same time, large vWf multimers appeared to be decreased. In contrast, samples anticoagulated with sodium citrate after DDAVP did not show a normalized vWf multimer pattern and were characterized by a persistently decreased vWf:CBA. Moreover, in all of the patients studied, platelet vWf presented normal vWf:CBA values in accordance with the normal levels and multimer organization of the vWf molecule. Our findings indicate that the collagen-binding defect displayed in vitro by type 2A vWf depends only on the lack of circulating large vWf multimers. Moreover, the observation of normal platelet vWf:CBA seems to indicate a primary role of plasma rather than platelet vWf in assuring platelet plug formation.

Adolescent↗
PubMed1997

Von Willebrand factor abnormalities in IgA nephropathy.

BACKGROUND: Plasma concentration of von Willebrand factor (vWF) has been used as an index of endothelial dysfunction. Increased release of vWF from endothelial cells has been reported in several conditions, and there is also evidence that dysfunctioning endothelial cells synthesize defective molecules. In fact, unusually large vWF multimers have been described and related to the pathogenesis of some microangiopathic diseases. Abnormal levels of vWF have been reported in primary glomerulitis, but this was no referred to histological diagnosis. Furthermore, no qualitative vWF analysis was performed in these glomerulopathies. Therefore the aim of our study was to analyse quantitatively and qualitatively vWF in patients with IgA (IgAN) and non-IgA mesangial proliferative glomerulonephritis (PGN). METHODS: Fourteen IgAN patients, eight PGN patients, seven subjects with different glomerulonephritides, and 10 healthy controls formed the basis of this study. On peripheral venous blood collected in the presence of protease inhibitors, vWF parameters were investigated. vWF antigenic activity (vWF:Ag) was measured by electroimmunodiffusion. vWF subunits mobility was studied by crossed immunoelectrophoresis (CIE) and in some patients vWF multimeric analysis was performed by SDS-agarose gel electrophoresis. RESULTS: Mean vWF:Ag was significantly higher in PGN patients as compared to controls, while there was no significant difference between PGN and IgAN patients and between IgAN and controls. CIE revealed a pre-peak in 12 of 14 IgAN patients and a migration index which did not differ between controls, IgAN, and PGN subjects. No pre-peak was observed in PGN and in other glomerulonephritides. Analysis of plasma vWF multimeric pattern by SDS-agarose gel electrophoresis disclosed in four IgAN patients abnormally large vWF multimers that were not documented in PGN subjects. CONCLUSIONS: This study, by showing the presence of a pre-peak and of large vWF multimers in IgAN patients, suggests an altered postsecretory handling of the vWF in IgAN and possibly a different role of the vWF in IgAN in respect to PGN.

Adult↗
PubMed1996

Abnormally large von Willebrand factor multimers in Henoch-Schönlein purpura.

Allergic vasculitis phenomena seem to be involved in Henoch-Schönlein purpura (HSP). Elevated plasma levels of von Willebrand factor (vWf) are a well recognized feature of vasculitis and have been taken as an indication of in vivo endothelial cell damage. Plasma factor VIII:C and vWf levels and vWf multimeric pattern were studied in 8 patients with HSP, during active disease and twice during the remission (3 and 9 months later). Plasma vWf multimeric composition was evaluated using low resolution gels which better resolve large vWf multimers. During active disease plasma factor VIII:C, vWf:Ag, and vWf:RCoF were normal in 5% of patients and increased in three, but in each patient, platelets appeared to aggregate at doses of ristocetin lower than in normals. Furthermore, all patients demonstrated the presence of abnormally large vWf multimers usually found only in platelets and endothelial cells. Three and 9 months later, during remission, in spite of the normalization of factor VIII:C and vWf levels, the abnormal multimers were still detectable, as well as hyper-responsiveness to ristocetin. These findings confirm that damage and/or perturbation of endothelial cells is associated with HSP. Moreover, the persistence of abnormality in the vWf multimeric pattern, when the disease is inactive, suggests that the mechanisms involved operate through the entire clinical course.

Adolescent↗
PubMed1996

DDAVP infusion in haemophilia A carriers: different behaviour of plasma factor VIII and von Willebrand factor.

1-desamino-8-D-arginine vasopressin (DDAVP) increases factor VIII (FVIII) and von Willebrand factor (vWF) levels in patients with haemophilia A and in some patients with von Willebrand disease. It is generally held that the increase of FVIII is a consequence of the increase of vWF. Carriers of haemophilia A generally, but not always, show plasma FVIII levels lower than vWF due to an abnormality in one of the two alleles of the FVIII gene. We investigated the time-course of plasma FVIII:C and vWF:Ag levels in 25 obligate carriers of haemophilia A after DDAVP infusion. In carriers with a normal FVIII to vWF ratio (> 0.8), DDAVP induced a progressive ratio decrease that reached levels significantly lower than that taken as cut-off to discriminate between low and normal values (0.68 +/- 0.1 vs before 0.912 +/- 0.18). In carriers with a borderline (0.7-0.8) or reduced (< 0.7) ratio DDAVP induced a further decrease in the FVIII/vWF ratio, albeit with a different kinetic; after an initial increase, values were lower than pre-DDAVP figures. In all subjects, following the post-DDAVP peak, plasma FVIII progressively decreased while vWF contemporaneously continued to increase. In contrast, DDAVP did not induce significant changes in the FVIII/vWF ratio in normal females, and the two molecules appeared to increase similarly throughout the observation period. These findings indicate that after DDAVP, FVIII increases less or for a shorter time than vWF, also in haemophilia A carriers who have a normal FVIII/vWF ratio. Hence, DDAVP may help identify haemophilia A carriers, especially subjects with normal or borderline ratios. Even though molecular biology procedures at present are the best and more reliable tools to identify the carrier state, DDAVP seems to improve the accuracy of haemostatic parameters.

Adult↗
PubMed1996

Inhibitory effect of prostacyclin and nitroprusside on type IIB von Willebrand factor-promoted platelet activation.

Von Willebrand disease (vWD) of type IIB is a hereditary haemorrhagic disorder characterised by an excessive interaction of von Willebrand factor (vWF) with the platelet receptor GPIb which promotes platelet activation and aggregation through a phospholipase A2-mediated release of arachidonic acid. The present report shows that prostacyclin and nitroprusside, vasodilator-compounds that enhance the cAMP and cGMP concentration respectively, cause a drastic inhibition of the type IIB vWF-induced platelet responses including increase of cytosolic Ca2+ concentration, phosphorylation of pleckstrin (47 kDa) and myosin light chain (20 kDa), secretion of ATP and serotonin, and aggregation parallel to a decrease of arachidonic acid release. Type IIB vWF also elicits tyrosine phosphorylation of proteins with apparent molecular mass of 60, 74, 82 and 130 kDa. Prostacyclin, which induces per se tyrosine-phosphorylation of proteins of about 38 and 45 kDa, inhibits drastically the type IIB vWF-promoted tyrosine-phosphorylation of the 74 kDa protein while inhibits slightly that of 60 kDa band. The protein tyrosine-kinase inhibitor genistein causes a little decrease in the type IIB vWF-induced release of arachidonic acid. It is concluded that the inhibition exerted by prostacyclin and nitroprusside on type IIB vWF-elicited platelet activation seems to be largely ascribable to prevention of the phospholipase A2 activation with the ensuing decrease of the subsequent protein tyrosine phosphorylation.

Epoprostenol↗
PubMed1995

Type IIB von Willebrand factor induces phospholipase A2 activation and cytosolic Ca2+ increase in platelets.

Von Willebrand factor (vWF) is a large glycoprotein which plays a central role in thrombus formation and blood clotting. The type IIB variant of vWF is characterized by an abnormally high affinity for the platelet receptor GPIb. Type IIB vWF purified from plasma and added to a platelet suspension induced a rapid, dose-dependent (1.2-9 micrograms/ml) increase in the cytosolic Ca2+ concentration. ATP secretion and platelet aggregation also occurred with type IIB vWF concentrations higher than about 5 micrograms/ml, which corresponds to the original plasmatic level. The IIB vWF-evoked (3 micrograms/ml) cytosolic Ca2+ increase was negligibly affected by ADP scavengers or protein kinase C inhibitors; it was drastically reduced by EGTA, La3+, Ni2+ or acetylsalicylate and abolished by the phospholipase A2 inhibitors ONO-RS-082 or oleolyloxyethyl-phosphocholine. Platelet exposure to IIB vWF caused arachidonic acid release, thromboxane B2 and inositoltrisphosphate formation. LJIB1, a monoclonal antibody against GPIb, completely suppressed all platelet responses, whereas LJCP8, an antibody against the receptor GPIIb-IIIa (alpha IIb beta 3 integrin), or the tetrapeptide RGDS, caused a complete inhibition of the aggregation but a partial inhibition of the activation-linked parameters. It is concluded that type IIB vWF-binding to GPIb induces phospholipase A2 activation, arachidonic acid release and GPIIb-IIIa dependent cellular Ca2+ influx. These events may lead to platelet secretion and aggregation.

Arachidonic Acid↗
PubMed1995

Different organization of von Willebrand factor oligomers in type-2A and -2B von Willebrand disease variants: effects of DDAVP infusion and protease inhibitors.

Plasma von Willebrand factor (vWf) displays a complex pattern of repeating multimers, whose heterogeneous size distribution seems to depend on the proteolytic cleavage of the constituent vWf subunit. Smaller vWf multimers are thought to derive by proteolytic cleavage of the larger forms. To clarify the relationship between large multimer representation and the structure of small vWf oligomers, DDAVP was infused in patients with type-2A and -2B von Willebrand disease (vWd) variants which lack circulating high vWf forms. Before infusion, high-resolution multimer analysis demonstrated a more pronounced representation of the satellite bands of each oligomer, mainly concerning fast-moving components, especially in type 2B vWd. After DDAVP, in type-2A vWd each oligomer displayed a different organization depending on whether restoration of large vWf multimers occurred. The lack of large vWf multimer restoration, as shown in citrated samples, was associated with the fast band being significantly more represented than the slower, and almost similar to the central component. In contrast, when the high-molecular-weight vWf forms were restored, as occurred in the samples collected in the presence of protease inhibitors, the relative representation of the fast- and slow-moving bands was similar to that of normal samples. In type-2B vWd, regardless of the anticoagulant used, DDAVP infusion did not restore large vWf multimers, and each oligomer displayed a significant increase in both the central band and fast-moving satellite, the fast being even more highly represented. These findings suggest that, regardless of the origin, the disappearance of large circulating multimers in type-2A and -2B vWd induces an increased representation of the fast-moving satellite of the low-molecular-weight multimers. Moreover, the time course of large and low/intermediate multimer decrease and increase provides a further demonstration that low vWf multimers derive from the larger ones, and that mainly the fast-moving band of the oligomer is involved.

Deamino Arginine Vasopressin↗
PubMed1995

Demonstration that venous occlusion fails to release von Willebrand factor multimers.

The acute simultaneous release of tissue plasminogen activator (t-PA) and von Willebrand factor (vWF) from endothelial cells in response to a variety of agonists including thrombin, DDAVP, histamine and adrenalin has been described. In the present study we investigated the effect of venous occlusion on the circulating levels of t-PA and vWF, as well as the molecular organization of vWF in 20 normal subjects. After occlusion a significant increase in plasma t-PA levels was observed even after the values were corrected for haemoconcentration. Venous occlusion also enhanced plasma vWF values, but the increase was abolished when the correction for haemoconcentration was introduced. Following venous occlusion, no circulating abnormally large vWF multimers were detected in the subjects studied. These forms are normally not present in the circulation and are released from endothelial cells through the regulated vWF pathway; their absence therefore seems to demonstrate that this pathway is not activated after venous occlusion. Since occlusion does not enhance vWF synthesis, the increase in vWF observed in the subjects investigated may be fully attributed to haemoconcentration.

Adult↗
PubMed1994

Re-evaluation of the therapeutic efficacy of DDAVP in type IIB von Willebrand's disease.

With few exceptions, 1-desamino-8-D-arginine vassopressin (DDAVP) has been shown to be useful in securing haemostasis in patients with von Willebrand's disease (vWd). In type IIB vWd, DDAVP has been reported to have no beneficial effects and to be contraindicated because it causes or worsens thrombocytopenia, due to in vivo platelet aggregation. Nevertheless, it was previously demonstrated that DDAVP may have clinical utility in some patients with type IIB vWd. Additional findings obtained in seven type IIB vWd patients of different kindreds undergoing minor surgical procedures are now reported. It was observed that DDAVP corrected the bleeding time in every case, with effects lasting for 2 h. Mean platelet counts decreased 30 min after DDAVP to variable degrees, depending on the anticoagulant used for blood collection, but were normal 2 h later. Furthermore DDAVP normalized FVIII, von Willebrand factor (vWf) antigen (vWf:Ag), and to a lesser extent, vWf ristocetin cofactor activity (vWf:RCoF). Intermediate and large vWf multimers appeared after 30 min. There were no bleeding complications during or after surgery, nor evidence of thrombosis. It was thus confirmed that DDAVP has clinical utility in the prevention of bleeding symptoms in different type IIB vWd patients. Therefore, despite the transitory thrombocytopenia and the incomplete restoration of larger vWf multimers, the use of this drug should be reconsidered for patients with type IIB vWd.

Deamino Arginine Vasopressin↗
PubMed1994

EDTA dependent pseudothrombocytopenia caused by antibodies against the cytoadhesive receptor of platelet gpIIB-IIIA.

AIMS: To clarify the mechanisms involved in the development of EDTA dependent pseudothrombocytopenia, particularly the platelet receptors. METHODS: Platelets were measured in 33 patients with pseudothrombocytopenia, using different anticoagulants to collect blood samples (direct test). The results were compared with the counts obtained by adding patients' serum or immunoglobulins to normal blood samples (indirect test). The role of platelet function was explored using ASA, PGE1, and apyrase as platelet inhibitors. The contribution of platelet receptor/s was investigated using antigens to gpIb-IX and gpIIb-IIIa monoclonal antibodies. Immunoglobulin class was estimated by the ability of IgG, IgA, and IgM antibodies to prevent platelet clumping. RESULTS: Agglutinating antibodies were IgA in 40%, IgG in 30%, and IgM in 10% of patients studied. Both patients' serum and immunoglobulins induced platelet clumping in normal samples anticoagulated with EDTA (indirect test). This was prevented by incubation of blood samples at 37 degrees C and almost completely inhibited by the platelet inhibitors ASA, PGE1, and apyrase. Pseudothrombocytopenia was also entirely prevented by an antigen to gpIIb-IIIa monoclonal antibody that recognises fibrinogen and the von Willebrand factor binding site. Pseudothrombocytopenia was almost completely abolished after the addition of RGD peptide, the recognition sequence of cytoadhesive proteins. CONCLUSIONS: These findings suggest that EDTA dependent pseudothrombocytopenia is caused by agglutinating antibodies that recognise cytoadhesive receptors on platelet gpIIb-IIIa and that an efficient platelet metabolism is required.

Adult↗
PubMed1994

Acquired factor VIII:C inhibitor in a patient with Sjögren's syndrome: successful treatment with steroid and immunosuppressive therapy.

A 57-year-old woman affected with Sjögren's syndrome without bleeding history developed spontaneous hematomas at the arms, the left foot and the thigh, cutaneous hemorrhages and hematuria. Routine coagulation tests showed a prolongation of activated partial thromboplastin time associated with a marked reduction of factor VIII activity (VIII: C 5%). Other deficiencies of blood coagulation factors, especially von Willebrand factor, were excluded. Measurement of factor VIII inhibitor revealed an activity of 26.4 Bethesda units/ml. These findings were consistent with the diagnosis of acquired hemophilia A due to the presence of a factor VIII inhibitor. The patient was treated with a combination of prednisone and azathioprine. The therapy led, in a few months, to a significant reduction of factor VIII: C inhibitor and she did not require replacement therapy. Furthermore, there was a complete remission of the bleeding tendency. Long-term therapy for about 3 years induced the complete disappearance of the inhibitor and a full normalization of coagulation tests.

Arm↗
PubMed1994

A new variant of von Willebrand's disease (type I Padua): doublet-organized plasma von Willebrand factor oligomers in the presence of all size multimers.

Type I von Willebrand's disease (vWd) is characterized by a concomitant decrease in plasma of von Willebrand factor antigen (vWf:Ag) and vWf ristocetin cofactor activity (vWf:RCoF), associated with the presence of all-size multimers. As a rule, there is no evidence of intrinsic abnormality in vWf. We describe a family with type I vWd with an abnormal plasma vWf multimer pattern. Analysis of plasma vWf multimeric structure by short-SDS-agarose gel electrophoresis showed an abnormal banding pattern for each vWf oligomer, which was organized as a doublet instead of the normal triplet. The electrophoretic mobility of each component appeared to be normal. Multimeric analysis on a long gel showed all the bands that were detectable in normal subjects, but unlike normals the fast moving satellite stained as the major component. The platelet vWf multimer pattern was normal. The infusion of DDAVP normalized vWf:Ag, vWf:RCoF and VIII:C, but not the abnormal multimer pattern observed on both short- and long-gel electrophoresis. The return of factor VIII/vWf complex to the baseline condition was more rapid than that observed in normal subjects or classic type I vWd patients. Analysis of the subunit fragments in the patients' plasma vWf demonstrated a relatively greater proportion, compared to the normal counterpart, of a 115(140)-kD fragment, which derives from the aminoterminal region of the mature molecule; in contrast, no intact subunit was detectable. These findings indicate a new, previously unreported, variant of type I vWd, which is characterized by plasma vWf oligomers organized as doublets, instead of triplets. The reduced post-DDAVP half-life, and the abnormal subunit fragments of vWf, suggest a molecule characterized by an increased susceptibility to proteolytic degradation. As a result, the decrease in circulating vWf levels may be due to an instability of the abnormal vWf, rather than, or in addition to, a decrease in its synthesis.

Adult↗
PubMed1993

Platelet aggregation induced by plasma from type IIB von Willebrand's disease patients is associated with an increase in cytosolic Ca2+ concentration.

The effect of type IIB von Willebrand's factor (vWF) on platelet cytosolic Ca2+ ion concentration, measured by means of the probe fura 2, was investigated. Seven patients with type IIB von Willebrand disease (vWD) were studied. Addition of type IIB vWD plasma to platelet suspensions induced a cytosolic calcium increase accompanied by platelet aggregation. Both processes were completely abolished by addition of the calcium-chelating agent EGTA, indomethacin, peptide RGDS, and monoclonal antibodies blocking the vWF binding site on GPIb-IX (LJIB1) or the cytoadhesive receptor on GPIIb-IIIa (LJCP8). The ADP-scavenger apyrase and the protein kinase C-inhibitor staurosporine partially inhibited the rate of the cytosolic calcium increase. No direct correlation between the extent of Ca2+ rise and the phenotypic expression of IIB vWD, such as the degree of spontaneous platelet aggregation or thrombocytopenia was apparent. It is suggested that aggregation and cytosolic Ca2+ increase in platelets exposed to plasma from type IIB vWD patients is mediated by a self-potentiating mechanism involving both GPIb and GPIIb-IIIa receptors as well as the thromboxane biosynthetic pathway.

Amino Acid Sequence↗
PubMed1993

Combined haemophilia A and type I von Willebrand's disease: a family study including an evaluation of the effects of DDAVP infusion.

A family with concurrent haemophilia A and type I von Willebrand's disease (vWd) is described. The propositus was affected by both disorders. The propositus' mother was an obligate carrier of haemophilia A being the daughter of a haemophilic. The father and sister were affected by vWd. The sister was also a possible carrier of haemophilia A. This is the first report of both disorders occurring simultaneously. The infusion of 1-desamino-8-d-arginine vasopressin (DDAVP) induced, in the propositus, a normalization of circulating levels of vWf, with a less pronounced enhancement of factor VIII:C. In the father, the response to DDAVP infusion of factor VIII/vWf complex was normal. In the mother, the time-course of factor VIII:C was characterized, after a peak at 30 min, by a progressive decrease until 2 hours after infusion, in contrast to vWf which appeared further increased at the same times. Therefore, the low factor VII:C/vWf:Ag ratio, already present before infusion, became significantly more pronounced 2 hours after DDAVP. Similar findings were observed in another obligate carrier of the family, in the propositus' sister and in 10 other haemophilia A carriers, belonging to different kindreds. In all patients, even when the basal factor VIII:C/vWf:Ag ratio was normal, two hours after DDAVP it decreased in agreement with the haemophilia A carrier state.

Adult↗
PubMed1993

Effect of recombinant-tissue plasminogen activator, low molecular weight urokinase and unfractionated heparin on platelet aggregation.

We studied the interaction of two thrombolytic agents, recombinant-tissue plasminogen activator (r-TPA) and low molecular weight urokinase (UK), with platelet aggregation in the absence or presence of unfractionated heparin (UH). With platelet rich plasma (PRP), a dose dependent inhibition was seen for both r-TPA and UK. However, this effect was more evident in the presence of r-TPA. UH did not modify this effect. However, it enhanced platelet aggregation induced by ADP and decreased the aggregation induced by collagen (COL) as already shown by us. With washed platelets, only r-TPA decreased platelet aggregation in a dose dependent manner in the presence of COL and only at the highest dose (100 micrograms) in the presence of TH. The presence of ten units of plasminogen (PLG) together with 10 micrograms of r-TPA or 1250 units of UK totally inhibited TH-induced platelet aggregation. UH reversed this effect. In contrast, when COL was the aggregating agent, the inhibition of platelet aggregation in presence of PLG, seems to be further increased by UH. Since UH is an adjunct of thrombolytic therapy to prevent rethrombosis, this double edged sword could partially explain the lack of therapeutic effect in some patients.

Adenosine Diphosphate↗