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Biomedical subjects

A Casonato

Publications and source records attributed to A Casonato.

At least 19 recordsLinked to original sources
PubMed1992

Urokinase-type plasminogen activator release after DDAVP in von Willebrand disease: different behaviour of plasminogen activators according to the synthesis of von Willebrand factor.

Nine healthy volunteers and 23 patients with various types of von Willebrand disease were studied before and after DDAVP infusion. We investigated the behaviour of factor VIII/von Willebrand factor measurements, and of tissue plasminogen activator and urokinase-type plasminogen activator. In mild von Willebrand disease the increase of both plasminogen activators was similar to that seen in normal controls. A different fibrinolytic behaviour was found in the type I platelet low and in the type III von Willebrand disease patients. An impaired and absent fibrinolytic response to DDAVP was seen in the former and in the latter von Willebrand disease, respectively. A close relation between either u-PA and t-PA or von Willebrand factor was observed. The possibility of a linkage among these three proteins was discussed.

Adolescent↗
PubMed1992

Detection of two missense mutations and characterization of a repeat polymorphism in the factor VII gene (F7).

The 3' portion of the coagulation factor VII gene, containing the activation and serine protease domains, was investigated in four subjects with factor VII deficiency by temperature gradient gel electrophoresis and sequencing of polymerase chain reaction (PCR) products. Molecules displaying an altered melting behaviour were detected in three subjects, and direct sequencing showed two mutations. A G-to-T transversion causing a missense mutation, Cys-310 to Phe, suppresses a disulphide bond conserved in the catalytic domain of all serine proteases. This mutation, which in the homozygous form causes a severe reduction in protease activity (4%), was found in two patients from different Italian regions. A G-to-A transition, which gives rise to a missense mutation, Arg-304 to Gln, and is associated with the factor VII padua variant, was found in the heterozygous form in a subject also affected by von Willebrand disease. Two polymorphic alleles, which differ in one repeat monomer element, were precisely mapped in a region spanning the exon-intron 7 border of the factor VII gene and studied in families with factor VII or X deficiency.

Base Sequence↗
PubMed1992

Impaired release of tissue plasminogen activator (t-PA) following DDAVP infusion in von Willebrand's disease with low platelet von Willebrand factor content.

Tissue plasminogen activator (t-PA) and von Willebrand factor (vWF) are both released by vascular endothelial cells after the infusion of DDAVP. Such release has not been observed in patients with severe von Willebrand's disease (vWD). In the present work we demonstrate that the degree of simultaneous DDAVP-induced release of t-PA and vWF, in patients with vWD, is strictly related to the platelet vWF content. Twelve patients with type I, and three patients with type III vWD were studied. The type I vWD group included three patients with reduced platelet vWF content (platelet-low) and nine patients with normal levels (platelet-normal). In all patients studied the plasma t-PA levels were within the normal range. No significant change in either t-PA or vWF was observed after DDAVP in the patients with undetectable levels of platelet vWF (type III vWD). A mild increase was found in those patients with type I platelet-low, while in type I platelet-normal vWD the response was similar to that observed in normal subjects. The release of the two molecules appeared, therefore, to be linked to platelet vWF content and the rates of increase in both t-PA and vWF were similar in each group of patients studied. Since platelets are regarded as a tissue compartment of vWF our findings seem to suggest that the presence of vWF and its release from endothelial cells is required for a normal concomitant release of t-PA. In contrast, post-DDAVP release of vWF seems to be independent from that of t-PA since it was normal in a patient with congenital deficiency of t-PA release.

Adolescent↗
PubMed1991

Effect of human recombinant erythropoietin on bleeding time, platelet number and function in children with end-stage renal disease maintained by haemodialysis.

We studied platelet number and function in nine anaemic children with end-stage renal disease during a clinical trial with recombinant human erythropoietin (rHu-EPO). All the children showed a correction in both haematocrit and haemoglobin levels which was followed by a significant reduction in bleeding time. We also observed a significant increase in platelet count after both 6 and 12 weeks of therapy; at the same time mean platelet volume decreased and a normal platelet mass was maintained. The mean baseline platelet aggregation response to ADP was normal, but was decreased to collagen (P less than 0.05 vs normal control). Platelet production of thromboxane B2 in serum was also lower than normal controls. After correction of anaemia with rHu-EPO, platelet aggregation improved in patients with a decreased baseline response, and mean levels of thromboxane B2 became normal. In conclusion, the treatment with rHu-EPO improved haemostatic balance not only by correcting anaemia, but also by increasing platelet count and function.

Adolescent↗
PubMed1991

Pregnancy-induced worsening of thrombocytopenia in a patient with type IIB von Willebrand's disease.

Thrombocytopenia has been reported in patients with type IIB von Willebrand's disease (vWd) during pregnancy. In the present work we report the behaviour of platelet count and von Willebrand factor (vWf) multimers in a pregnant type IIB vWd patient who presented with mild thrombocytopenia in the steady state. The evolution of pregnancy was associated with a progressive decrease of platelet count which showed its lowest value two days before delivery (20 x 10(9)/l). The tendency of the platelet count to decrease was suddenly reversed a few days later (77 x 10(9)/l). At the same time, the vWf multimeric pattern showed a strict but inverse correlation with the platelet count. In fact, a progressive increase in low and intermediate sized vWf multimers, which proceeded until platelets reached their minimum level, was noted. A few days after delivery, concomitant with the prompt platelet increase, low and intermediate multimers became decreased. During pregnancy, the patient's platelet showed additional increased responsiveness to ristocetin but did not demonstrate spontaneous platelet aggregation (SPA). On the contrary, the patient's plasma, collected both during and after pregnancy, caused normal platelets to aggregate spontaneously. SPA appeared completely blocked by an anti-GPIIb-IIIa monoclonal antibody (MAb), which recognized the binding site for fibrinogen, vWf and fibronectin. In contrast, a MAb against ristocetin-induced vWf binding site on GPIb did not affect SPA. These findings suggest that the common stimulus or stimuli, responsible for the pregnancy-induced decrease of platelet count and improvement of vWf multimeric pattern in type IIB vWd is strictly related to pregnancy.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Discrepant increase in factor VIII: C and von Willebrand factor after DDAVP infusion in a patient with variant von Willebrand's disease.

We have studied a patient with von Willebrand's disease (vWd) whose von Willebrand factor (vWf) multimer patterns showed significant decreases of all but the major fast moving vWf multimer (promoter). Bleeding time (BT) was very prolonged, there was almost no ristocetin-induced platelet aggregation (RIPA) and vWf levels were very low. The factor VIII: C/vWf: Ag ratio appeared to be higher than normal because of the relatively increased concentration of factor VIII: C. The infusion of DDAVP normalized BT, improved RIPA and restored normal factor VIII: C levels, these effects lasted for 5 h even though only a slight increase of vWf: Ag and vWf: RCoF was observed. RIPA was completely inhibited by an anti-glycoprotein (GP) Ib monoclonal antibody that recognizes the ristocetin-induced vWf binding site. Plasma vWf multimer analysis revealed only slight increases of all components and an additional, more pronounced representation of vWf protomer. These data suggest that the patient has an abnormal vWf molecule characterized by a greater ability to carry factor VIII than would be expected from the vWf levels. Furthermore, since the vWf protomer was the only significant vWf component present both before and after DDAVP infusion we hypothesize that some of the haemostatic functions of the patient's vWf may depend on it.

Bleeding Time↗
PubMed1990

1-Desamino-8-D-arginine vasopressin (DDAVP) infusion in type IIB von Willebrand's disease: shortening of bleeding time and induction of a variable pseudothrombocytopenia.

We have investigated the effects of 1-desamino-8-D-arginine vasopressin (DDAVP) infusion on platelet count and bleeding time in 4 patients with type IIB von Willebrand's disease (vWd). Three of four patients showed a normalization of the bleeding time within 1 h after the infusion, while bleeding time was not modified in the fourth. In accordance with the literature, thrombocytopenia was observed after DDAVP infusion, but this thrombocytopenia was due to the anticoagulants used for blood collection. In two patients (F.I., G.F.) no thrombocytopenia was observed when platelets were counted by fingerstick method but there was a 20% platelet decrease in blood samples collected in sodium citrate and a 50% decrease in samples collected in EDTA. Dramatic falls in platelet counts (70-95%) were observed in the additional two patients (C.A., D.Z.) after DDAVP infusion, when both sodium citrate or EDTA were used as anticoagulants. In the latter two patients there was also a 50% decrease in platelet count when the fingerstick method was used. The decrease in the patient's platelet count in EDTA samples after DDAVP infusion could be prevented, in part, by the previous additions of an anti GPIb monoclonal antibody and an anti GPIIb-IIIa monoclonal antibody. Thus, the thrombocytopenia observed in the four IIB vWd patients studied after DDAVP infusion seems to be, at least partially, a pseudothrombocytopenia depending on the calcium concentration in the blood samples and the availability of GPIb and GPIIb-IIIa receptors. These findings and the normalization of the bleeding time observed in three of the four patients has led us to reconsider the possible use of DDAVP in the treatment of our IIB vwd patients.

Anticoagulants↗
PubMed1990

A de novo and heterozygous gene deletion causing a variant of von Willebrand disease.

An abnormal von Willebrand factor (vWF) gene restriction pattern has been found in a patient with von Willebrand disease. Because this gene alteration is not present in his parents or in 50 normal and 25 affected subjects, and the restriction fragment length polymorphism haplotypes are inherited normally in the patient's family, we suggest that a de novo mutation is present. Bands with reduced intensity and additional fragments, observed in several restriction digests, hybridize with noncontiguous copy DNA (cDNA) portions, thus indicating the presence of a heterozygous gene deletion. The deletion removes a genomic region containing at least codons 1147 through 1854 and corresponding to the D3-A3 homologous protein domains. The extent of the vWF pseudogene on chromosome 22 is roughly similar to that of the deleted area. However, the pseudogenic nature of the deletion is excluded by the mapping of bands with reduced intensity in the patient to the true vWF gene. The vWF antigen levels are one fourth of normal and ristocetin cofactor activity is severely impaired. The reduction of high molecular weight multimers in plasma and platelets and the altered triplet morphology are compatible with the presence of a dominant variant of type II von Willebrand disease.

Bleeding Time↗
PubMed1990

Characterization of polymorphic markers in the von Willebrand factor gene and pseudogene.

Three TaqI restriction fragment length polymorphisms (RFLP) detected by the central portion of von Willebrand factor cDNA, which recognizes the true gene and in addition pseudogenic sequences, were characterized and mapped. Small cDNA fragments which hybridized with DNA from families with von Willebrand disease were used. Two of the RFLP, recognized by 1.7 and 0.45 kb cDNA fragments, are not in linkage either with von Willebrand disease or with RFLP located in the von Willebrand factor (vWF) gene, which indicates their pseudogenic location. These markers located in 22q11, near to the bcr gene, provide new tools for the study of several somatic and constitutional alterations affecting this chromosomal region. The third RFLP is recognized by a cDNA fragment corresponding to the N-terminal portion of mature vWF and is localized in the true gene. Since significant linkage disequilibrium with other informative RFLP is not present, this marker contributes to the definition of family haplotypes associated with von Willebrand disease.

Blotting, Southern↗
PubMed1990

Platelet aggregation and pseudothrombocytopenia induced by 1-desamino-8-D-arginine vasopressin (DDAVP) in type IIB von Willebrand's disease patient.

Our study shows that the thrombocytopenia described in type IIB von Willebrand's disease (vWd) after 1-desamino-8-D-arginine vasopressin (DDAVP) infusion is, at least partially, a pseudothrombocytopenia. There was a discrepancy in platelet counts in blood anticoagulated with EDTA (less than 10 x 10(3)/microliters) or citrate (55 x 10(3)/microliters) in one patient with type IIB vWd and chronic thrombocytopenia (80 x 10(3)/microliters) after DDAVP infusion. Furthermore, DDAVP induced a normalization of patient's prolonged bleeding time. Spontaneous platelet aggregation (SPA) observed in platelet-rich plasma before DDAVP infusion was inhibited completely by monoclonal antibodies which block binding of fibrinogen, vWf and fibronectin to GPIIb-IIIa. SPA was partially inhibited by a monoclonal antibody which blocks the binding of vWf to GPIb. After DDAVP, in contrast, SPA partially persisted in the presence of anti-GPIIb-IIIa monoclonal antibodies but was completely inhibited by anti-GPIb monoclonal antibody. Therefore GPIb and GPIIb-IIIa complex seem to play a different role in SPA before and after DDAVP infusion into type IIB vWd.

Adult↗
PubMed1990

Distinct abnormalities in the interaction of purified types IIA and IIB von Willebrand factor with the two platelet binding sites, glycoprotein complexes Ib-IX and IIb-IIIa.

We have studied the interaction of the congenitally abnormal type IIA and IIB von Willebrand factor (vWF) molecules, both lacking the larger multimeric forms, with the two vWF binding sites on platelets, the glycoprotein (GP) Ib-IX and GP IIb-IIIa complexes. Variant as well as normal (N) vWF were purified from plasma. Estimates for binding of subunit molecules per platelet at saturation (Bmax) and dissociation constant in moles/liter (Kd), respectively, were obtained from binding isotherms of 125I-labeled vWF, with the following results. In the presence of ristocetin (binding to GP Ib-IX): N, 25,693 and 0.5 x 10(-8); IIA, both parameters not measurable; IIB, 17,708 and 0.87 x 10(-8). After thrombin stimulation (binding to GP IIb-IIIa): N, 17,059 and 1.12 x 10(-8); IIA, 23,751 and 4.87 x 10(-8); IIB, 19,890 and 2.52 x 10(-8). Distinct experiments based on measuring the ability of the variant species (from the same patients and one additional IIB patient) to inhibit the binding of normal 125I-vWF to platelets gave results in agreement with those reported above. Other studies showed that only IIB vWF bound to platelets in the absence of any mediating substance (Kd = 5.21 x 10(-8) mol/liter and Bmax = 9,599 subunits per platelet) and induced aggregation at a concentration of 10 micrograms/ml (3.6 x 10(-8) M). Thus, IIB vWF binds to GP Ib-IX with high affinity and induces platelet aggregation, whether with or without ristocetin, in spite of the absence of larger multimers. In contrast, the binding of IIA vWF to GP Ib-IX occurs with very decreased affinity, and this defective function may result from specific structural abnormalities rather than just being a reflection of the absence of larger multimeric forms. Both IIA and IIB vWF exhibit decreased affinity for GP IIb-IIIa. In this case, the extent of the defect correlates with the absence of larger multimers.

Blood Platelets↗
PubMed1990

Effect of cellulose acetate 0.2 micron filter on platelet specific proteins plasma levels.

We are reporting the effect of a cellulose acetate 0.20 micron filter (Flow Pore D26) on preparation of platelet poor plasma (PPP) for subsequent assay of platelet specific proteins. PPP was obtained using the Edinburgh anticoagulant mixture and a centrifugation at 2,300 g for 20 minutes. The mean levels of platelet factor 4 (PF4) and beta-thromboglobulin (beta TG) before filtration were: PF4 15.7 ng/ml (1.5-42.8 ng/ml); beta TG 62.0 ng/ml (25-140 ng/ml). After filtration we obtained: PF4 4.8 ng/ml (1.0-8.9 ng/ml), beta TG 28.4 ng/ml (8.5-51.1 ng/ml). Thus difference for both the platelet specific proteins was statistically significant (p less than 0.005). The contamination by platelet-like material was also greatly affected by the filter (before filtration 4.3 x 10(6)/ml), (2-15 x 10(6)/ml), after filtration 2.0 x 10(6)/ml (1-5 x 10(6)/ml), p less than 0.005). If a high speed centrifuge is not available, the use of this simple filter method could avoid falsely elevated values of platelet specific proteins.

Adult↗
PubMed1990

"Anti-platelet antibodies" in HIV infected haemophiliacs.

We have studied anti platelet antibodies and circulating immunocomplexes in 16 haemophiliacs with mild thrombocytopenia eight of which were infected by human immunodeficiency virus (HIV). No difference in platelet count was observed between HIV+ (143 +/- 31 x 10(9)/l) and HIV- patients (148 +/- 30 x 10(9)/l). On the contrary, HIV+ haemophiliacs had serum platelet bindable IgG (SPBIgG), normal platelet associated IgG (PAIgG), high serum IgG and circulating immunocomplexes (CIC). Considering all 16 patients serum IgG correlated with CIC (r = 0.7 p less than 0.01) and SPBIgG (r = 0.6 p less than 0.01) respectively. We obtained also a positive correlation between serum CIC and SPBIgG (r = 0.51 p less than 0.05). Immunoblotting of patients' sera showed no specific binding to target platelet antigens. In conclusion there is no evidence of HIV related immune thrombocytopenia in our haemophiliacs but the study confirms the appearance of immunocomplexes in the HIV+ subjects.

Adult↗
PubMed1989

A new congenital platelet abnormality characterized by spontaneous platelet aggregation, enhanced von Willebrand factor platelet interaction, and the presence of all von Willebrand factor multimers in plasma.

A case is reported of a 49-year-old woman with a mild bleeding tendency. Her bleeding time, platelet count and size, plasma ristocetin cofactor activity, von Willebrand factor (vWF) antigen, and vWF multimeric pattern are all within normal limits. Spontaneous platelet aggregation is observed when citrated platelet-rich plasma (PRP) is stirred in an aggregometer cuvette. This aggregation is completely is only slightly diminished by an antiglycoprotein (GP) IIb/IIIa or by an anti GPIb monoclonal antibody. The patient's PRP shows increased sensitivity to ristocetin. The distinct feature of this patient, also present in two family members studied, is that platelet aggregation is initiated by purified vWF in the absence of any other agonist. The vWF-induced platelet aggregation is abolished by anti-GPIb and anti-GPIIb/IIIa monoclonal antibodies and by EDTA (5 mmol/L). Apyrase inhibits the second wave of aggregation. Patient's platelets in PRP are four to six times more reactive to asialo vWF-induced platelet aggregation than normal platelets. The amount of radiolabeled vWF bound to platelets in the presence of either low concentration of ristocetin or asialo vWF was increased 30% compared with normal. The patient's platelet GPIb was analyzed by SDS page and immunoblotting and by binding studies with anti-GPIb monoclonal antibodies showed one band with slightly increased migration pattern and a normal number of GPIb molecules. Unlike the previously reported patients with pseudo or platelet-type von Willebrand disease, this patient has normal vWF parameters.

Antibodies, Monoclonal↗