fibrinopeptide-b and Afibrinogenemia

Topics: Afibrinogenemia; Amino Acid Sequence; Blood Coagulation; Blood Coagulation Tests; Carbohydrates; Factor XIII; Fibrinogen; Fibrinolysin; Fibrinopeptide A; Fibrinopeptide B; Genetic Variation; Humans; Macromolecular Substances; Peptide Fragments; Thrombin; Transglutaminases

A large number of families have now been described in whom affected individuals have within their plasmas an abnormal species of fibrinogen (factor I). These defects, presumably examples of the phenomenon of allotypy--i.e., the synthesis of variant forms of a normal protein--have been inherited as autosomal dominant characteristics. In the great majority of cases, clotting is abnormally slow when thrombin is added to the abnormal plasma. Sometimes this defect appears to reside in impaired release of fibrinopeptides by thrombin. In other cases, fibrinopeptide release proceeds normally, but aggregation of fibrin monomers is impeded. In the latter instance, aggregation may be abnormally slow or, once it begins, it may proceed at a normal rate. Curiously, a bleeding tendency is more likely to occur in patients in whom fibrinopeptide release is impaired, while dehiscence of operative wounds rarely complicates dysfibrinogenemias associated with impaired aggregation of fibrin monomers; thrombosis has been described in both groups of patients. Most of the reported cases may be distinguished by functional criteria and by the physicochemical behavior and biochemical nature of the abnormal protein. Additonally, one family has been described in which plasma clots abnormally rapidly upon addition of thrombin, and two others in which crosslinking of fibrin by fibrin-stabilizing factor (factor XIII) is defective.

Topics: Afibrinogenemia; Amino Acid Sequence; Blood Coagulation Disorders; Child; Diagnosis, Differential; Female; Fibrinogen; Fibrinopeptide A; Fibrinopeptide B; Genes, Dominant; Humans; Male

We found two heterozygous dysfibrinogenemias, designated fibrinogen Kosai and fibrinogen Ogasa. Kosai was associated with arteriosclerosis obliterans but Ogasa showed no bleeding or thrombotic tendencies. The plasma fibrinogen concentrations from the two propositi (Ogasa and Kosai) were much lower when determined by the thrombin-time method (0.94 and 1.06 g L(-1), respectively) than when determined by the immunological method (2.87 and 2.72 g L(-1), respectively). We performed DNA sequencing and functional analyses to clarify the relationship between the structural and functional abnormalities. Genetic analysis of PCR-amplified DNA from the propositi identified the heterozygous substitution Bbeta15Gly-->Cys (GGT-->TGT). Western blotting analysis of purified fibrinogen revealed the existence of albumin-fibrinogen complexes. Functional analyses indicated that compared with the normal control, the propositi's fibrinogen released only half the normal amount of fibrinopeptide B and showed markedly impaired polymerization. In addition, the observation of thinner fibers in fibrin clots (by scanning electron microscopy) indicated markedly defective lateral aggregation in the variant fibrinogens. The impaired functions may be due to the substitution of Cys for Bbetao15Gly plus the existence of some additional disulfide-bonded forms.

Topics: Adult; Afibrinogenemia; Amino Acid Substitution; Batroxobin; Female; Fibrinogens, Abnormal; Fibrinopeptide B; Humans; In Vitro Techniques; Microscopy, Electron, Scanning; Middle Aged; Point Mutation; Thrombin

We investigated the molecular basis of hypofibrinogenemia in a man with a normal thrombin clotting time. Protein analysis indicated equal plasma expression of 2 different Bbeta alleles, and DNA sequencing confirmed heterozygosity for a new Bbeta235 P-->L mutation. Protein analysis also revealed a novel gamma(D) chain, present at a ratio of 1:2 relative to the gamma(A) chain. Mass spectrometry indicated a 14 d decrease in the gamma(D)-chain mass, and DNA sequencing showed this was caused by a novel gamma82 A-->G substitution. DNA sequencing established heterozygosity for 2 further mutations: T-->C in intron 4 of the Aalpha gene and A-->C in the 3' noncoding region of the Bbeta gene. Studies on the man's daughter, together with plasma expression levels, discounted both the Aalpha and Bbeta mutations as the cause of the low fibrinogen, suggesting that the gamma82 mutation caused the hypofibrinogenemia. This was supported by analysis of 31 normal controls in whom the Bbeta mutations were found at polymorphic levels, with an allelic frequency of 5% for the Bbeta235 mutation and 42% for the Bbeta 3' untranslated mutation. The gamma82 mutation was, however, unique to the propositus. Residue gamma82 is located in the triple helix that separates the E and D domains, and aberrant packing of the helices may explain the decreased fibrinogen concentration. (Blood. 2000;95:1709-1713)

Topics: 3' Untranslated Regions; Afibrinogenemia; Aged; Alleles; Amino Acid Sequence; Amino Acid Substitution; Chromatography, High Pressure Liquid; DNA Mutational Analysis; Female; Fibrinogen; Fibrinogens, Abnormal; Fibrinopeptide B; Hematoma; Hernia, Inguinal; Heterozygote; Humans; Introns; Male; Molecular Sequence Data; Peptide Mapping; Point Mutation; Postoperative Complications; Protein Conformation

A congenitally abnormal fibrinogen was isolated from the blood of a young woman with a severe bleeding diathesis. Coagulation tests showed a prolonged Thrombin and Reptilase time partially corrected by Ca2+. Polymerization of thrombin induced preformed fibrin monomers was severely impaired. Thrombin caused the release of fibrinopeptides with normal retention times on HPLC. However, the rate of release was abnormally slow and the total amount of fibrinopeptide A (FpA) released reached only approximately 50% of the theoretical maximum. The rate and quantity of FpA release was normal when Reptilase was used. Transmission Electron Microscopy (TEM) of Thrombin induced clots showed an altered clot structure characterized by a reduced mean fiber diameter. The mother has a polymerization defect similar to the propositus, her fibrinopeptide release is unaffected however. The father has a minor fibrinopeptide release defect suggesting the presence of two populations of fibrinogen. This study supports the idea that the fibrinogen isolated from the propositus has two defects inherited as separate genetic traits. This fibrinogen has been named Fibrinogen Guarenas I.

Topics: Adolescent; Afibrinogenemia; Biopolymers; Female; Fibrin; Fibrinogens, Abnormal; Fibrinopeptide A; Fibrinopeptide B; Hemorrhagic Disorders; Humans; Kinetics; Male; Metrorrhagia; Microscopy, Electron; Thrombin; Thrombin Time

Congenital dysfibrinogenemia was found in two non related and asymptomatic families. Low levels of plasma fibrinogen were found using a chronometric assay but normal levels were found using both an immunologic method and a method to measure the fibrin formed after two hours incubation with thrombin. Kinetic analysis of fibrinopeptide release revealed a delay in the thrombin catalyzed release of fibrinopeptide B from both abnormal fibrinogens. Timed release of fibrinopeptide A was normal. Analysis of fibrinopeptides by high-performance liquid chromatography showed the same retention times in both normal and abnormal fibrinogens. Polymerisation of fibrin monomers and the sialic acid content per mol of fibrinogen were normal. Although these cases seem similar, until their structural defects are determined, it is proposed to provisionally designate them fibrinogens Madrid I & II.

Topics: Afibrinogenemia; Blood Coagulation Tests; Chromatography, High Pressure Liquid; Female; Fibrin Fibrinogen Degradation Products; Fibrinogen; Fibrinogens, Abnormal; Fibrinopeptide B; Humans; Middle Aged; N-Acetylneuraminic Acid; Plasminogen; Protein Conformation; Sialic Acids; Thrombin; Tissue Plasminogen Activator

Incubation of fibrinogen Seattle II with thrombin (17 mu/ml) resulted in the release of two forms of fibrinopeptide A (FpA) which were resolved by high-performance liquid chromatography. Amino acid analysis disclosed that the abnormal FpA contained histidine in place of arginine. At lower, approximately physiologic thrombin concentrations only half the normal amount of FpA was released, and fibrinopeptide B (FpB) release was delayed. The effect of this substitution on the time course of fibrinopeptide release is consistent with conclusions drawn from other studies on the kinetics of fibrinopeptide release, viz., that prior removal of FpA is not required before FpB hydrolysis by thrombin, and that optimal rates of FpB release occur after formation of fibrin I polymer.

Topics: Afibrinogenemia; Amino Acids; Arginine; Chromatography, High Pressure Liquid; Fibrinogen; Fibrinogens, Abnormal; Fibrinopeptide A; Fibrinopeptide B; Histidine; Humans; Thrombin; Time Factors