title: Electron microscopy of fibrin Paris I.
abstract: Fibrinogen Paris I, a congenital fibrinogen abnormality, is characterized by delayed fibrin aggregation and poor clot retraction owing to the replacement of normal gamma-chains by mutant gamma-chains, which are termed gamma-Paris I. Available evidence indicates that the structural abnormality involves the amino acid sequence near the COOH-terminus of the mutant chain and probably includes the region containing the normal gamma-chain crosslinking site. Electron microscopy was carried out on Paris I fibrin. In place of the normally interwoven network of branching cross-striated fibers, negatively or positively contrasted Paris I fibrin was characterized by nonfibrous clumps of material connected by distince fibrous strands tending to be thinner and more irregular in width than normal fibrin. Most Paris I fibrin fibers tended to the aperiodic, although cross-striations were observed occasionally in negatively contrasted specimens and rarely in positively contrasted specimens. In addition, Paris I fibrin frequently showed relatively short, abruptly terminating fibers. The gross ultrastructural differences between normal and Paris I fibrin suggest that for fibrin assembly to take place normally, a region(s) in the fibrin molecule near to or possibly overlapping the COOH-terminal gamma-chain crosslinking site must be preserved or at least not sterically hindered.
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D005337:Fibrin; D005340:Fibrinogen / Q000032:analysis / Q000235:genetics*; D006801:Humans; D008854:Microscopy, Electron; D009154:Mutation; D011487:Protein Conformation; D011498:Protein Precursors / Q000235:genetics
chemical_list: D000596:Amino Acids; D011498:Protein Precursors; D005337:Fibrin; D005340:Fibrinogen