1/5. Fibrinogen brescia: hepatic endoplasmic reticulum storage and hypofibrinogenemia because of a gamma284 Gly-->Arg mutation.The proposita suffered from liver cirrhosis and biopsy showed type 1 membrane-bound fiberglass inclusions. The hepatic inclusion bodies were weakly periodic acid-Schiff diastase-positive, and on immunoperoxidase staining reacted specifically with anti-fibrinogen antisera. Coagulation investigations revealed low functional and antigenic fibrinogen together with a prolonged thrombin time of 37 seconds (normal, 17 to 22 seconds) suggestive of a hypodysfibrinogenemia. dna sequencing of all three fibrinogen genes showed a single heterozygous mutation of GGG (Gly)-->CGG (Arg) at codon 284 of the gamma-chain gene. However, examination of purified fibrinogen chains by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, reverse-phase high-performance liquid chromatography, ion-exchange high-performance liquid chromatography, and isoelectric focusing, failed to show any evidence of the mutant gamma(Br) chain in plasma fibrinogen. This finding was substantiated by electrospray ionization mass spectrometry, which showed only a normal gamma (and Bbeta) chain mass, but a large increase in the portion of their disialo isoforms. We speculate that misfolding of the variant protein causes hepatic retention and the subsequent hypofibrinogenemia, and that the functional defect (dysfibrinogenemia) results from hypersialylation of otherwise normal Bbeta and gamma chains consequent to the liver cirrhosis. These conclusions were supported by studies on six other family members with hypofibrinogenemia, and essentially normal clotting times, who were heterozygous for the gamma284 Gly-->Arg mutation.- - - - - - - - - - ranking = 1keywords = chromatography (Clic here for more details about this article) |
2/5. Hypofibrinogenemia due to novel 316 Asp --> Tyr substitution in the fibrinogen Bbeta chain.We investigated the molecular basis of hypofibrinogenemia in a woman with a plasma fibrinogen of 1.0 mg/mL. After sequencing the coding region and intronic boundaries of all three fibrinogen genes a single heterozygous GAC-->TAC mutation was identified at codon 316 of the Bbeta gene. This Asp-->Tyr substitution segregated with the hypofibrinogenemia in the only other affected family member. Examination by SDS-PAGE, isoelectric focussing, reverse phase chromatography and electrospray ionisation (ESI) mass spectrometery, failed to detect expression of the new Bbeta chain in purified plasma fibrinogen. The absence of the variant chain was confirmed by ESI tryptic mapping; while the [M 1 H] and [M 2 H] ions of the affected peptide (MGPTELLIEMEDWK) were clearly visible at 1,692 and 847 m/z, there were no new signals (1,741 or 871 m/z) that would at indicate expression of the variant in plasma. Asp 316 and its gamma chain homologue (Asp 252) are conserved in all known species and this is the first report of a mutation at either of these. The residue appears to be critical in maintaining the structure of the five stranded sheet that forms the dominant structural feature of the D domains.- - - - - - - - - - ranking = 0.5keywords = chromatography (Clic here for more details about this article) |
3/5. Two cases of dysfibrinogenemia characterized by abnormal FPB release: fibrinogen Madrid I & II.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.- - - - - - - - - - ranking = 0.5keywords = chromatography (Clic here for more details about this article) |
4/5. Fibrinogen Osaka IV: a congenital dysfibrinogenemia found in a patient originally reported in relation to surgery, now defined to have an A alpha arginine-16 to histidine substitution.We discovered a congenital heterozygous dysfibrinogen in a patient and reported this case in relation to surgery some time ago (Jpn J Surg (1988) 18:43-46). Further studies on the isolated abnormal population of fibrinogen derived from this patient have revealed that fibrinopeptide a was not cleaved by ancrod, a snake venom-derived thrombin-like enzyme, but by thrombin, slowly but completely. The released fibrinopeptide a components, being the A, AY, and AP peptides, were all found to be abnormal, as evidenced by slightly earlier elution positions on high-performance liquid chromatography, compared with the normal counterparts. By analyzing their amino acid sequence, we have identified an arginine to histidine substitution at position 16 of the A alpha chain, the thrombin cleavage site. Utilizing insolubilized abnormal fibrinogen, we confirmed that the polymerization site assigned to the central E domain, the "A" site, was exposed by thrombin, but not by ancrod. This dysfibrinogen, designated as fibrinogen Osaka IV, is the second abnormal molecule with an A alpha arginine-16 to histidine substitution identified among Japanese families.- - - - - - - - - - ranking = 0.5keywords = chromatography (Clic here for more details about this article) |
5/5. Severe coagulopathy after a bite of a green bush viper (Atheris squamiger): case report and biochemical analysis of the venom.A 34 year old male bitten by an adult Atheris squamiger snake developed symptoms of nausea, vomiting, diarrhea which were followed by drowsiness and impaired breathing. Local hemorrhage, edema and pain at the bite-site occurred, but no systemic bleeding or hemorrhagic diathesis developed. All clinical and laboratory parameters were in the normal range except for afibrinogenemia, thrombocytopenia and slight proteinuria. Replacement therapy (fibrinogen and platelet concentrates) and treatment of shock stabilized the patient within 2d and coagulation returned to normal. Atheris squamiger venom was subjected to biochemical and biological analysis. The LD50 of the venom was 5 mg/kg (mice, s.c.). It produced local hemorrhage corresponding to about 25% of the activity of puff adder venom (Bitis arietans). in vitro the venom had a fibrinogen-converting activity, it did not activate purified prothrombin but very likely contained a F V and Ca2 -dependent prothrombin activator. The venom exhibited strong platelet-aggregating activity, which was not inhibited by protease inhibitors and by EDTA or EGTA. The venom also aggregated acetylsalicylic acid treated platelets indicating, that the arachidonic acid pathway was not essential for activation. Rat serum rapidly inhibited the platelet-aggregating activity of the venom; human serum, however, had only a partial inhibitory effect. Preliminary experiments showed that platelet-aggregating activity may be separated from fibrinogen-converting activity by anion-exchange chromatography.- - - - - - - - - - ranking = 0.5keywords = chromatography (Clic here for more details about this article) |