Changes in fibrinogen and fibrin induced by a peptide analog of fibrinogen gamma365-380.

BACKGROUND: The effects of synthetic peptides with sequences derived from the gamma-chain of fibrinogen on the functional properties of fibrinogen and fibrin were investigated. METHODS: Methods included thrombelastography, clot turbidity measurement, clot elasticity measurement, platelet aggregation, and scanning transmission electron microscopy (STEM). RESULTS: Peptide gamma369-380 (NH(2)-WATWKTRWYSMK-COOH) showed the greatest impact on fibrin structure, compared with the 76 other overlapping dodecapeptides. Addition of this peptide, or peptide gamma365-380 (NH(2)-NGIIWATKTREWYSMK-COOH) to a mixture of fibrinogen and thrombin resulted a shorter clotting time, higher clot turbidity, lower clot elastic modulus, a higher degree of D-trimer and D-tetramer formation, and impaired plasmin proteolysis of the clot. In STEM, fibrin formed in the presence of peptide gamma369-380 consisted of a more extensive array of linear fibrils typically consisting of 20 or more molecules. Fibrils were better organized than those from non-peptide containing mixtures. CONCLUSIONS: Replacement of the tryptophan residue gamma376 massively reduced the effect of the peptide on fibrin structure. Binding of the peptide to fibrinogen induces conformational changes, which result in accelerated clotting and increased lateral association of fibrin protofibrils. The results imply a relevant functional role of sites interacting with peptide gamma369-380 region in the fibrinogen molecule.

Open-label non-randomized versus double-blind randomized antidepressive treatment: what are the advantages of clinical decision over randomization?

OBJECTIVE: To study, whether and how the results from open and double-blind randomized trials on antidepressants differ. METHODS: Seventy-one patients were included in a study comparing open, non-randomized, standardized treatment with paroxetine (PAROX) and amitriptyline (AMI) after a minimum of six drug-free days (OPEN). A second group of 56 patients received the same treatment under blind-randomized conditions (BLIND-RANDOM). The course of psychopathology as assessed by the Hamilton Depression Rating Scale was compared using repeated measurements ANOVA-(rm). RESULTS: While the rate of adverse events was higher in the BLIND-RANDOM compared to the OPEN condition, completer-analyses revealed no differences in psychopathological outcome. CONCLUSIONS: With similar clinical outcome BLIND-RANDOM trials of antidepressants may expose depressed patients to an increased risk of adverse events, when compared to OPEN conditions. However, the clinical outcome in study completers did not differ between the BLIND-RANDOM and the OPEN condition. Thus, the psychiatrist's choice may have impact on adverse events rather than on clinical outcome of antidepressant treatment.