Search PubMed⌕ Search

Biomedical subjects

M Furlan

Publications and source records attributed to M Furlan.

At least 109 records · Page 6Linked to original sources
PubMed1990

Fibrinogen Geneva, a new case of A alpha 16 Arg----Cys dysfibrinogenaemia.

A new congenital variant of fibrinogen, from which only half the normal amount of fibrinopeptide A can be released by thrombin, was found in three members of a family having no major bleeding or thrombotic tendency. Following carboxamidomethylation of the reduced fibrinogen chains, an abnormal peptide was cleaved by thrombin from the amino terminus of the A alpha-chain (A* alpha 1-19) and isolated by reversed phase high-performance liquid chromatography. Amino acid analysis indicated the presence of carboxymethyl cysteine in this A alpha-chain fragment which in normal fibrinogen is devoid of cysteine. We conclude that fibrinogen Geneva is another fibrinogen variant with the substitution A alpha 16 Arg----Cys.

Blood Coagulation Tests↗
PubMed1989

How high is the true fibrinogen content of fibrinogen standards?

A number of tests are available to measure plasma fibrinogen. Of these, the determination of the thrombin induced rate of plasma clotting is the most widely used in a clinical laboratory. Quantitative fibrinogen assays are calibrated with commercially available standards. There exists no internationally recognized standard against which the manufacturers could calibrate their fibrinogen preparations and lyophilized normal plasmas. In the present study, the amount of clottable material was determined in ten commercially available fibrinogen standards. Following clotting with thrombin, the fibrin clots were extensively washed with citrated saline and subjected to nitrogen analysis. The proportions of intact and partially degraded fibrinogens in each standard were determined by SDS-polyacrylamide gel electrophoresis of the washed clots. Knowing the amino acid composition and the relative proportions of these fractions, the nitrogen contents of the clots were converted to fibrinogen. More than 30% deviation from the declared values was observed in three standards, in one of them even 80%. Our results indicate that fibrinogen standards of markedly differing quality are commercially available and that an accurate, international standard for fibrinogen assay should be established.

Blood Coagulation↗
PubMed1989

[Hemostasis parameters in 55 patients with venous and/or arterial thromboembolisms].

55 consecutive patients (28 males and 27 females) who had suffered from (recurrent) venous and/or arterial thromboembolism were evaluated for laboratory findings of thrombophilia. At the time of investigation, 15 patients were taking oral anticoagulants. In addition to patient and family history and clinical examination, a coagulation profile, euglobulin clot lysis time before and after venous occlusion, assays of plasminogen, antithrombin III, protein C (PC), free protein S (PS[f]), and C4b binding protein bound protein S (PS[b]) were obtained. 2 patients not orally anticoagulated had partial PD deficiency with functional PC activity values of 53% and 57% respectively, as compared to normal human plasma (NHP). Functionally active PS(f) was found to be lower than normal in 14 patients not taking oral anticoagulants and without signs of hepatopathy. In 4 of these 14 patients partial PS deficiency was present (PS[f] between 7 and 37% of NHP, and PS[b] between 51 and 86% of NHP). In one of these 4 subjects the hereditary nature of PS deficiency was proven by investigation of family members. In 3 of the 14 patients a shift from PS(f) (between 34 and 66%) towards PS(b) (124-141%) was found. The remaining 7 patients showed subnormal PS(f) values (56-64%) and normal PS(b) values (78-105%). In the patients receiving oral anticoagulant therapy, PC and PS levels were diminished. Statistically there was no close relationship between PC and PS levels on the one hand and prothrombin time values on the other. In anticoagulated patients, therefore, PC or PS deficiency can only be diagnosed by investigation of members of the propositus's family.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

[Comparison of a sensitive rabbit brain thromboplastin and a human placenta thromboplastin for thromboplastin time determination].

Prothrombin times were measured in 120 orally anticoagulated patients and 122 patients not orally anticoagulated using two different commercial thromboplastin reagents, a rabbit brain thromboplastin (CRB-Thromboplastin, Roche) and a human placenta thromboplastin (Thromborel S, Behring). A good correlation (r = 0.93, slope = 1.089, intercept = 0.014) was found between the International Normalized Ratio (INR) values of the anticoagulated plasmas obtained with both thromboplastins. Defining five degrees of intensity of anticoagulation (between INR less than or equal to 2.0 to INR greater than or equal to 5.1) the intensity of treatment was judged concordantly with both thromboplastins in 67% of the patients and as differing by one degree in 32%. In only one out of 120 patients was a larger discrepancy of INR values found. - A good correlation (r = 0.93) was also found between the prothrombin times expressed as Quick percentage values as assessed with both thromboplastins in 122 patients not orally anticoagulated. In 82 cases a "normal" prothrombin time (Quick greater than or equal to 70%) and in 33 cases a "subnormal/diminished" percentage value (Quick less than 70%) was obtained with both thromboplastins. In only 7 out of 122 plasma samples was the Quick percentage normal with one and subnormal with the other reagent. - The good conformity of the INR values measured with two thromboplastins of differing species but similar sensitivity (International Sensitivity Index [ISI] = 1.14 for CRB-Thromboplastin, and = 1.10 for Thromborel S) supports the recommendation by the World Health Organization that the intensity of oral anticoagulation be expressed in terms of INR. Whether INRs obtained with thromboplastins of largely differing ISIs show sufficient conformity will need to be assessed by further prospective studies.

Animals↗
PubMed1988

Isolation of fibrinogen A alpha-chain by affinity chromatography on concanavalin A-sepharose.

A method was developed for isolation of the A alpha-chain from S-carboxamidomethylated fibrinogen. A mixture of the three constituent polypeptide chains of human fibrinogen was applied onto a column of concanavalin A-Sepharose. While the carbohydrate-free A alpha-chain was not delayed on the affinity chromatography column, both glycosylated subunit chains, B beta- and gamma-chain, were adsorbed to the insolubilized lectin and were quantitatively eluted from the column with 0.2 M methyl-alpha-D-mannoside. SDS-electrophoresis on polyacrylamide gel was employed for analysis of chromatographic fractions. Complete recovery of the A alpha-chain was observed. The described procedure is very simple and permits isolation of large amounts of pure A alpha-chain from S-carboxyamidomethylated fibrinogen.

Chromatography, Affinity↗
PubMed1988

[Measurement of bleeding time and study of thrombocyte aggregation. Standardization of methods, normal values and results in patients with suspected hemorrhagic diathesis].

Bleeding time measurement and investigation of platelet aggregation in platelet rich plasma (PRP) are routine procedures for the diagnosis of defects in primary hemostasis. These tests are subject to methodological difficulties and should be well standardized in each individual laboratory. - In the present study, bleeding time was measured using the Simplate II device in 40 normal subjects. Furthermore, platelet aggregation in PRP induced by ADP, collagen, arachidonate, and ristocetin was examined. 26 patients referred for investigation of a suspected mild bleeding disorder, who had a normal plasmatic coagulation profile, a normal von Willebrand factor activity, and a normal platelet count, were similarly studied. - Based on the reference values established in the 40 normal subjects, platelet aggregation was found to be pathologic in 7 patients and normal in 12. In 7 patients platelet aggregation was considered to be borderline-pathologic as defined by the range of platelet aggregability found in the 10% of our normal subjects showing the weakest aggregation responses. Bleeding time was prolonged in only 3 patients whereas it was normal in the remaining 23. There was strong evidence of a hemostatic defect as assessed by systematic patient history in 6 out of 7 patients with pathologic platelet aggregation, but in only 3 out of 19 showing normal or borderline-pathologic aggregation. - Pathologic platelet aggregation, therefore, represents not only an abnormal laboratory finding but is likely to be associated with a hemorrhagic diathesis. Platelet aggregation studies do not permit etiologic diagnosis of the thrombocytopathy except for the well-defined membrane glycoprotein deficiencies. The bleeding time appeared to be of low sensitivity for the diagnosis of mild platelet dysfunction.

Adolescent↗
PubMed1988

Modified in vivo platelet retention test for evaluating primary haemostasis.

We present a modified in vivo platelet retention test for evaluating platelet plug formation in a standardized incision applied to the skin (template bleeding time). In contrast to previously published similar procedures we determined platelet retention at defined time intervals. The investigation of 20 healthy subjects with this method revealed a characteristic biphasic pattern of platelet consumption at the wound surface, which could be correlated with primary and secondary platelet aggregation. In 10 patients with congenital platelet dysfunction and 2 patients with von Willebrand's disease the pattern of platelet retention was affected principally in its early phase, whereas aspirin, when given to 2 healthy subjects, inhibited platelet retention predominantly in its late phase. Our modified platelet retention test provides information about dynamic events associated with platelet plug formation in both normal and disordered primary haemostasis and may also be useful for evaluating in vivo effects of antithrombotic drugs.

Adolescent↗
PubMed1987

[Von Willebrand's disease].

Von Willebrand's disease (vWD), one of the most frequent hereditary bleeding disorders, is associated with a deficiency or a defective structure of von Willebrand factor (vWF). The defect is transmitted by autosomal inheritance. vWF is a plasma glycoprotein which mediates platelet adherence to the subendothelium of the injured blood vessel and is thus indispensable for primary hemostasis. vWF is composed of identical subunits linked together by disulfide bridges. Each subunit contains binding site(s) for factor VIII, collagen and platelets. The highly polymeric vWF factor is the largest known plasma protein. Functional activity is preferentially associated with the largest multimeric forms of vWF. Binding of vWF onto collagen fibrils activates its platelet binding sites, which are apparently not accessible in circulating vWF. Aggregation of washed fixed platelets in the presence of ristocetin or collagen is used for assessment of vWF's biological activity. Important additional information for the diagnosis of vWD is provided by the antigen assay and by electrophoretic analysis of the multimeric pattern of vWF. In type I vWD, all polymeric forms of vWF are reduced in the same proportion, while only the largest, i.e. the most active, multimers are deficient in type II vWD. The most severe type III vWD is characterized by an undetectable concentration of vWF. DDAVP corrects the prolonged bleeding time in patients with mild forms of vWD. Cryoprecipitate or "virus inactivated" factor VIII concentrates are employed for substitution therapy. Our results suggest that the newly introduced "virus inactivated" factor VIII concentrate from SRK is likewise suitable for this purpose.

Deamino Arginine Vasopressin↗
PubMed1987

[A modified in vivo platelet retention test in the evaluation of primary hemostasis].

A simple assay system for measuring platelet retention in a standardized superficial skin wound is presented. Platelets were counted in the blood collected at the site of the wound 1, 2 and 3 minutes following incision. Per cent platelet retention was calculated from the difference between venous blood platelet count and wound blood platelet count, divided by venous count. The time course of platelet retention, measured in 20 healthy persons, reflected the sequence of primary and secondary platelet aggregation. Ten patients with congenital platelet defects already showed impaired platelet retention in the early stage of bleeding. On the other hand, administration of aspirin to 10 healthy subjects inhibited only the late stage of platelet retention. In comparison with the template bleeding time our platelet retention test provides additional information useful for evaluating congenital and drug-induced defects in platelet plug formation.

Aspirin↗
PubMed1987

Monitoring of heparin therapy with the activated partial thromboplastin time and chromogenic substrate assays.

Heparin therapy was monitored with the activated partial thromboplastin time (APTT) and with chromogenic substrate assays (factor Xa and factor IIa inhibition) in 100 plasma samples from 47 patients. Heparin concentrations were classified as being below, within or above a defined therapeutic range (TR; 0.2-0.55 units heparin/ml). In a first group of patients (A), all three assays allocated the plasma heparin levels to the same concentration interval with respect to the TR. The most frequent diagnoses in group A were uncomplicated arterial or venous thromboembolism, myocardial infarction with limited tissue necrosis, cardiac surgery without major complications and successfully treated infectious disease. In a second group of patients (B), the results of APTT suggested higher heparin concentrations with respect to the TR than the chromogenic assays. Predominant diagnoses were severe infectious diseases, severe liver disorders, extensive myocardial infarction and postoperative complications after cardiac surgery. The discrepancy between heparin concentrations determined by either APTT or the chromogenic substrate assays is most likely due to a non-heparin related prolongation of APTT caused by the underlying disease.

Chromogenic Compounds↗
PubMed1987

Exposure of platelet binding sites in von Willebrand factor by adsorption onto polystyrene latex particles.

Von Willebrand factor molecules are flexible linear polymers composed of repeating protomeric polypeptide subunits. In the process of primary hemostasis, von Willebrand factor promotes platelet adhesion and platelet plug formation at the site of vascular injury. This biologic activity is apparently related to the multimeric size of von Willebrand factor. We simulated von Willebrand factor binding to the subendothelial surface by adsorbing purified human von Willebrand factor onto polystyrene latex particles of two different diameters, i.e., 0.312 micron and 2.02 micron. The rate and extent of 125I-labeled von Willebrand factor binding to polystyrene was similar with both size classes of latex particles. The von Willebrand factor-coated latex beads of 2.02 micron diameter, in contrast to the smaller size, induced rapid agglutination of formalin-fixed human platelets in the absence of any other aggregating agent. Von Willebrand factor was also adsorbed from human plasma onto latex particles coated with anti-von Willebrand factor antibodies. Again, only the large beads, carrying the von Willebrand factor-antibody complex, induced agglutination of fixed platelets. Shear stress promoted the rate of von Willebrand factor adsorption to latex particles. Our results suggest that adsorption to surface exposes binding sites in human von Willebrand factor for platelets.

Adsorption↗
PubMed1986

Three abnormal fibrinogen variants with the same amino acid substitution (gamma 275 Arg----His): fibrinogens Bergamo II, Essen and Perugia.

We report on three unrelated individuals with the same uncommon type of dysfibrinogenemia, originating from Bergamo, Essen and Perugia. None of them showed bleeding symptoms while the Bergamo patient and members of her family presented with a thrombotic tendency. The presence of a defective fibrinogen was suggested by prolonged thrombin and reptilase times. Furthermore, fibrinogen concentrations of less than 0.28 g/L were determined by the functional assay whereas values of 1.5-2.4 g/L were measured by heat precipitation or electroimmunoassay. Fibrinogen was isolated by affinity chromatography on insoluble fibrin monomer. The rate of fibrinopeptide release by thrombin was normal while the fibrin polymerization reaction was strongly delayed. An abnormal peptide (gamma 265-310) was isolated by high-performance liquid chromatography after cyanogen bromide cleavage of the purified gamma-chain of fibrinogen Bergamo II and Essen. The same peptide was also isolated following cyanogen bromide treatment of the intact fibrinogen Perugia. Sequence analyses of these peptides demonstrated the same amino acid exchange in all three fibrinogens: gamma 275 arginine----histidine. The described fibrinogen variants appear to possess a molecular defect which has thus far only been observed in fibrinogen Haifa.

Amino Acid Sequence↗
PubMed1986

[Monitoring heparin therapy by thrombin time and activated partial thromboplastin time--a comparison].

In 106 plasma samples obtained from patients on heparin therapy, monitoring by 2 methods (activated partial thromboplastin time and thrombin clotting time--APTT and TT) was compared. All patients in whom APTT indicated markedly higher plasma heparin concentrations than the TT were critically ill (group B): their main diagnoses included severe infectious disease, severe liver disease and extensive myocardial infarction. Patients with lesser discrepancies between the results of APTT and TT did not suffer from such severe conditions (group A). Cardiac surgery without major postoperative problems, limited myocardial infarction and uncomplicated thromboembolism were the main diagnoses in this group. In group B, non-heparin related prolongation of APTT was thought to be the main factor responsible for the overestimation of plasma heparin concentrations by this test. We conclude that in patients with severe infectious disease, liver disease or extensive tissue necroses (i.e. myocardial infarction), APTT cannot be recommended for laboratory monitoring of heparin therapy.

Blood Coagulation Tests↗
PubMed1986

[A new test for evaluating the von Willebrand factor: collagen-induced agglutination of fixed thrombocytes].

In primary hemostasis von Willebrand factor (vWf) promotes the adhesion of platelets to subendothelial structures of the damaged blood vessel. A new test is described which measures the collagen binding affinity of vWf. Activities of vWf in plasmas of 51 patients were measured with either collagen (ColCof) or ristocetin (RCof). Regression-analysis showed a good correlation of both activities (r = 0.924). In a second group of 21 patients with a variant of von Willebrand's disease, ColCof activity was generally higher than RCof activity.

Collagen↗
PubMed1986

[Binding of the von Willebrand factor to solid surfaces: effect of shear strength].

Platelet adhesion onto subendothelium of a damaged blood vessel depends upon the presence of von Willebrand factor (vWf) only at high flow shear rate. Our results showed enhanced adsorption of vWf onto stainless steel and latex surfaces under conditions of high shear stress, thus suggesting that in the rapidly flowing blood the extremely long vWf molecules are stretched, thus accelerating their binding to a given surface.

Factor VIII↗