Search PubMed⌕ Search

Biomedical subjects

A Girolami

Publications and source records attributed to A Girolami.

At least 397 records · Page 22Linked to original sources
PubMed1986

von Willebrand factor interaction with the glycoprotein IIb/IIa complex. Its role in platelet function as demonstrated in patients with congenital afibrinogenemia.

We have studied three afibrinogenemic patients, who had only trace amounts of plasma and platelet fibrinogen as measured by radioimmunoassay, and demonstrate here that the residual aggregation observed in their platelet-rich plasma is dependent upon von Willebrand factor (vWF) binding to the platelet membrane glycoprotein (GP)IIb/IIIa complex. The abnormality of aggregation was more pronounced when ADP, rather than thrombin, collagen, or the combination of ADP plus adrenaline was used to stimulate platelets. With all stimuli, nevertheless, the platelet response was completely inhibited by a monoclonal antibody (LJP5) that is known to block vWF, but not fibrinogen binding to GPIIb/IIIa. Addition of purified vWF to the afibrinogenemic plasma resulted in marked increase in the rate and extent of aggregation, particularly when platelets were stimulated with ADP. This response was also completely blocked by LJP5. Addition of fibrinogen, however, restored normal aggregation even in the presence of LJP5, a finding consistent with the knowledge that antibody LJP5 has no effect on platelet aggregation mediated by fibrinogen binding to GPIIb/IIIa. Two patients gave their informed consent to receiving infusion of 1-desamino-8-D-arginine vasopressin (DDAVP), a vasopressin analogue known to raise the vWF levels in plasma by two- to fourfold. The bleeding time, measured before and 45 min after infusion, shortened from greater than 24 min to 12 min and 50 s in one patient and from 16 min to 9 min and 30 s in the other. Concurrently, the rate and extent of ADP-induced platelet aggregation improved after DDAVP infusion. The pattern, however, reversed to baseline levels within 4 h. The concentration of plasma vWF increased after DDAVP infusion, but that of fibrinogen remained at trace levels. We conclude that vWF interaction with GPIIb/IIIa mediates platelet-platelet interaction and may play a role in primary hemostasis.

Adenosine Diphosphate↗
PubMed1986

Platelet factor 4 (PF4) and heparin released platelet factor 4 (HR-PF4) in diabetes mellitus. Effect of the duration of the disease.

Several investigators have reported an altered platelet function in diabetes mellitus as measured by elevated levels of platelet specific proteins platelet factor 4 (PF4) and B-thromboglobulin (BTG). We studied 20 insulin dependent (IDD), 20 non insulin dependent (NIDD) diabetic males without overt clinical symptoms of cardiovascular disorders and 30 normal controls. We evaluated PF4, BTG and heparin released platelet factor 4 (HR-PF4) as measured 2.5 minutes after a bolus injection of 5,000 I.U. of a commercial mucous heparin. The patients showed normal levels of both PF4 and BTG. Furthermore HR-PF4 failed to show statistically significant variation between patients and controls. However when the diabetics were divided on the basis of the duration of the disease, the IDD had an increased HR-PF4 mean level and the trend became statistically significant when diabetes existed more than 17 years (patients HR-PF4 149.1 ng/ml, range 17.3-194; controls HR-PF4 110.9 ng/ml range 50-160, less than p less than 0.05). NIDD failed to reveal the same pattern. Although the significance of HR-PF4 is unknown, insulin dependent diabetes mellitus after many years could cause a potentially dangerous, silent vascular damage with enhanced platelet vessel wall interaction as measured by an elevated HR-PF4.

Adolescent↗
PubMed1986

Greater decrease of fibrinogen as compared to antithrombin III in L-asparaginase treated leukemia patients.

Fibrinogen and Antithrombin III (AT III) were studied sequentially during remission induction with L-asparaginase, prednisone and vincristine in 20 children with acute lymphoblastic leukemia (ALL). The first 2 weeks of therapy were characterized by significant decreases in plasma concentration of fibrinogen (p less than 0.05 or p less than 0.01). AT III (antigen and activity) decreased between the first and second week of therapy, but on an average, they remained a little above the lower limits of normal. However, at the second week, the difference was significant from basic values (p less than 0.05). All parameters gradually returned to normal after completion of L-asparaginase therapy.

Acute Disease↗
PubMed1986

A critical evaluation of the available methods for the determination of factor VIII von Willebrand.

Von Willebrand factor (vWf) is the major component of the circulating factor VIII complex. The von Willebrand molecule includes factor VIII related antigen (VIIIR: Ag) which represents the molecular substrate of the von Willebrand activity expressed as Ristocetin cofactor (VIIIR:RCoF) activity. Several methods have been developed for VIIIR: Ag evaluation, among the first being the rocket-immunoelectrophoresis method of LAURELL. Radial immunodiffusion (MANCINI's method) was also used. Subsequently, radioimmunological assays, either as radioimmunoassay (RIA) or immunoradiometric assay (IRMA), were developed with improvements in sensitivity, so that levels of VIIIR: Ag lower than 0.1% of normal can be detected. More recently, an enzyme-linked immunosorbent assay (ELISA), characterized by the use of enzyme-conjugated antibody was proposed. This method shows a sensitivity similar to immunoradiometric methods but without using any dangerous reagent. Finally, a nephelometric method was proposed for factor VIII antigen evaluation. For a qualitative evaluation of von Willebrand factor crossed-immunoelectrophoresis and multimeric analysis can be used. In the first case, the use of precipiting antibodies against von Willebrand factor may demonstrate a peak with different characteristics related to the biochemical property of von Willebrand. Multimeric analysis in SDS-agarose gel electrophoresis followed by staining with labelled antifactor VIII antibodies gives information about different polymeric forms of circulating VIII/vW factor. Von Willebrand factor activity, expressed as its ability to induce platelet aggregation in the presence of the antibiotic Ristocetin, can be carried out using normal formalin fixed platelets, either with aggregometer or visual methods (glass slide test or tubes test and microtritation plate). The corrected evaluation of factor VIII complex by all these techniques together with the clotting activity assay allows a satisfactory study of factor VIII properties.

Enzyme-Linked Immunosorbent Assay↗
PubMed1986

Dental extraction in congenital hemorrhagic patients.

125 dental extractions were performed in patients with hemophilia A, B, von Willebrand disease and rare coagulopathies. The missing factor was brought to a level of 15-40% according to the degree of surgical trauma. In the majority of cases a single pre-extraction administration of concentrate was sufficient. Antifibrinolytics were administered to the patients (tranexamic acid, 60 mg/kg/day) for 8-10 days. After tooth extraction, a fibrin sponge was positioned using anti-traumatic cross suture. In 90% of cases there was no bleeding, in the others modest easily controllable hemorrhagic episodes. Our results show that it is sufficient in hemophilia A and B to use low doses of antihemophilic concentrate (10-20 U/kg) and frequently a single pre-extraction administration. In rare coagulopathies the hemostatic procedure and dental management have also to be similar to those used in hemophilia A and B.

Adult↗
PubMed1986

Lack of antiplatelet activity of the new coumarin derivative 8-monochloro-3-beta-diethylaminoethyl-4-methyl-7-ethoxy- carboxylmethoxycoumarin under in vivo conditions in man.

Antiplatelet properties of AD 6 (8-monochloro-3-beta-diethylaminoethyl-4-methyl-7-ethoxy-carboxyl- methoxycoumarin) have been studied in vitro and in vivo. The drug showed a marked inhibitory effect on platelet aggregation, beta-thromboglobulin (beta TG) release and thromboxane B2 (TxB2) production in vitro. However, such effects were seen only in the presence of high concentrations of the drug (10(-3) and 10(-4) mol/l) and completely disappeared at lower concentrations. No effect was seen in vivo following oral administration of 300 mg of the drug in a small group of volunteers. It can be concluded that in vitro properties of the drug cannot be surmised without due caution to indicate its potential clinical use.

Adenosine Diphosphate↗
PubMed1986

Effects on platelets and on the clotting system of four glycosaminoglycans extracted from hog mucosa and one extracted from aortic intima of the calf.

A commercial heparin preparation, a heparin fraction with a molecular weight of 12,000 Daltons, heparan sulfate, dermatan sulfate obtained from hog mucosa, and mesoglycan, an heparinoid obtained from calf aortic intima were investigated. Commercial mucous heparin had a stimulatory effect on platelet aggregation induced by ADP, while the others failed to do so. Dermatan sulfate had a dose dependent inhibition and commercial mucosal heparin, a dose dependent stimulation, on serotonin release induced by ADP. Both the commercial mucosal heparin and dermatan sulfate showed an inhibition and the other glycosaminoglycans (GAGs) a negligible effect on collagen induced platelet aggregation. The collagen induced serotonin release was clearly reduced by all GAGs; heparan sulfate had this activity only at the highest doses used. Commercial mucosal heparin produced the highest activity on clotting systems as measured by activated partial thromboplastin time, while mesoglycan had the strongest anti-factor Xa specific activity as measured by a clotting assay. Dermatan sulfate was the weakest on both assays. When we injected intravenously an equivalent amount (about 60 mg) of heparin fraction, heparan sulfate, dermatan sulfate and mesoglycan in three different volunteers with an interval of 20 days after each injection, we had an immediate platelet factor 4 (PF4) release only with heparin fraction, heparan sulfate and mesoglycan. Heparin fraction and mesoglycan, in spite of having a wide discrepancy in anticoagulant effect, caused almost the same PF4 release. GAGs which can neutralize PF4 and which can also have specific anti-factor Xa activity could represent a great advantage in thrombosis prophylaxis.

Animals↗
PubMed1985

Disappearance of human platelet factor 4 (PF4) in rabbits: does an immediate component exist?

Twelve male New Zealand rabbits were injected with 21 micrograms/kg of human platelet factor 4 antigen (PF4). The decay of the protein followed a monoexponential curve for the first 5 mins, with a half-life (t 1/2) of 1.94 mins and a calculated concentration at 0 time (CO) of 79.4 ng/ml. Five rabbits were pre-treated with heparin (2.500 I.U. i.v.) and 3 mins later were injected with the same amount of PF4. PF4 decay followed a monoexponential curve with a t 1/2 of 25.3 mins, and with CO of 380.8 ng/ml. This value is not greatly different from the one calculated assuming an immediate and uniform distribution in plasma (482.7 ng/ml for a plasma volume of 43.5 ml/kg). The 12 rabbits injected with PF4 were divided in 3 groups, in which heparin was given at 10', 30' or 60' after PF4, respectively. After heparin the peak levels of PF4 were 139.9 ng/ml, 65.3 ng/ml and 52.7 ng/ml, respectively. The following monoexponential PF4 decay had t 1/2 of 20.7, 25.6 and 26.0 mins, respectively. In a separate group of 4 animals, we studied heparin decay after an intravenous bolus of 2.500 I.U. Heparin decay could not be described by a monoexponential equation and was different from the decay of PF4 injected after heparin. On the basis of the present data we suggest the presence of an immediate component of PF4 decay, most likely due to uptake by the tissues. Heparin pretreatment may avoid this uptake process.

Animals↗
PubMed1985

Antithrombin III activity and concentration in diabetes mellitus.

Antithrombin III (AT III) levels have been reported to be low, normal, and high in diabetes mellitus. Furthermore, a discrepancy between AT III activity and antigen concentration was reported. We have evaluated the behaviour of AT III activity and antigen level both in type 1 and type 2 diabetes, either in uncontrolled or in well controlled patients. AT III activity and antigen levels showed values similar to normal. No difference was seen between type 1 and type 2 diabetes. Similar results were observed in the group of well controlled diabetic patients. AT III activity and antigen did not correlate with blood glucose and glycosylated haemoglobin (HbA1). No difference was observed between AT III activity and antigen levels in any group. Therefore the hypercoagulable state found in diabetes mellitus does not depend on AT III modifications. A discrepancy between AT III activity and antigen was not confirmed. A dysantithrombinaemia, explained on the basis of an inactivation of protein glycosylation in diabetes mellitus has not been confirmed.

Adult↗
PubMed1985

Further studies on the hypercoagulable state of patients with Cushing's syndrome.

Factors XII, XI, IX and VIII, plasminogen and alpha 2-antiplasmin levels were found to be increased in a group of patients affected by Cushing's syndrome. High activity of these coagulation factors could be due to their increased release and synthesis mediated by cortisol. A significant correlation between the main arterial pressure and either factor VIII antigen, ristocetin cofactor or factor XII activity was found. Moreover a similar correlation between factor XII activity and either factor VIII antigen or ristocetin cofactor was seen. In conclusion, the presence of a hypercoagulable state in Cushing's syndrome seems confirmed. Synergic release of factor XII and factor VIII from endothelium could be due to high blood vessel tone secondary to hypercorticism. Finally, decreased fibrinolytic activity was suspected according to plasminogen and alpha 2-antiplasmin increase.

Blood Coagulation Disorders↗
PubMed1985

The effect of low-dose estroprogestinic preparations on prothrombin complex factors: no significant increase after an 8-month trial.

The behavior of the prothrombin complex factors in 16 healthy women during low-dose estroprogestinic treatment (laevonorgestrel 0.15 mg and ethynilestradiol 0.30 mg) at basal conditions and during 8 months of therapy has been investigated. We found a statistically significant decrease of the PTT (Partial Thromboplastin Time). The prothrombin time, on the other hand, became slightly decreased, but not to a statistically significant extent. Among the prothrombin time derived tests for evaluating the prothrombin complex only the PP test (Prothrombin Proconvertin test) was significantly shortened. Of the coagulation factors (factors II, VII and X) only a modest, but not statistically significant, increase in Factor VII and Factor X was noted. We conclude that, during the 8 month observation period, prothrombin complex factors are not altered substantially.

Adult↗
PubMed1985

Captopril-induced changes on active and inactive renin in a patient with factor XII congenital deficiency.

A linkage between prorenin, renin, and intrinsic coagulation systems has been suggested recently. We studied the behavior of renin, prorenin, and kallikrein in a patient affected by congenital factor XII deficiency. Captopril test, upright posture, and furosemide administration provoked in our patients changes of renin and prorenin similar to those found in normal and hypertensive subjects. Unchanged kallikrein levels confirmed that no interaction between prorenin activation and factor XII-kallikrein system appears to be present.

Adult↗
PubMed1985

Interaction of purified type IIB von Willebrand factor with the platelet membrane glycoprotein Ib induces fibrinogen binding to the glycoprotein IIb/IIIa complex and initiates aggregation.

Von Willebrand factor (vWF) was purified from the plasma of a patient with type IIB von Willebrand disease (vWF from such a patient, IIB vWF) who had a normal platelet count and showed no evidence of spontaneous platelet aggregation. Large multimers of IIB vWF were absent from purified preparations and from plasma. Ristocetin-induced platelet aggregation was enhanced by purified IIB vWF. The aggregation of washed normal platelets mixed with IIB vWF (0.4 microgram/ml) required lower amounts of ristocetin than the aggregation of normal platelets mixed with the same concentrations of normal vWF. Moreover, purified IIB vWF alone induced aggregation of platelet-rich plasma at concentrations as low as 10 micrograms of IIB vWF/ml in the absence of any other agonist. Aggregation was blocked by a monoclonal antibody against the platelet membrane glycoprotein, GPIb, as well as by an anti-GPIIb/IIIa antibody. Washed platelet suspensions were promptly aggregated by IIB vWF only when fibrinogen and CaCl2 were added to the mixture. Purified IIB vWF induces the binding of fibrinogen to platelets. Such binding was blocked by the anti-GPIb monoclonal antibody as well as by the anti-GPIIb/IIIa monoclonal antibody that inhibited aggregation. A second anti-GPIIb/IIIa antibody, which has the property of blocking vWF but not fibrinogen binding to platelets, blocked neither aggregation nor fibrinogen binding induced by IIB vWF. These studies demonstrate that platelet aggregation is triggered by the initial interaction of IIB vWF with GPIb which is followed by exposure of fibrinogen binding sites on GPIIb/IIIa. Fibrinogen binds to these sites and acts as a necessary cofactor for the aggregation response.

Antibodies, Monoclonal↗