Fibrin curves

There is a learning curve associated with the use of fibrin sealant and the application devices which are used to apply the agent can significantly influence... 

Fig. 63. Dependence of (S2)1 on M for fibrin initiated by thrombin at 37 °C (- -) curve 1 gives the theoretical dependence for a single strand, curve 3 shows the behavior of fibres with many strands parallel, and curve 2 is the best fit224 ...

The kinetics of the lytic effect displayed by the complexes of immobilized heparin with thrombin and fibrinogen, in distinction from those with plasmin, are described by their saturation curves. The observed slowing down of the dissolution of unstabilized fibrin is probably due to the inhibiton of the lytic activity of the complexes by the soluble products of the reaction. In fact, as it was shown in Ref. 106, further addition of immobilized heparin-protein complex to partially hydrolyzed fibrin results in a complete recovery of the dissolution rate. 

The blood coagulation cascade. Each of the curved red arrows represents a proteolytic reaction, in which a protein is cleaved at one or more specific sites. With the exception of fibrinogen, the substrate in each reaction is an inactive zymogen except for fibrin, each product is an active protease that proceeds to cleave another member in the series. Many of the steps also depend on interactions of the proteins with Ca2+ ions and phospholipids. The cascade starts when factor XII and prekallikrein come into contact with materials that are released or exposed in injured tissue. (The exact nature of these materials is still not fully clear.) When thrombin cleaves fibrinogen at several points, the trimmed protein (fibrin) polymerizes to form a clot. 

Mihalyi (1954b) studied in a similar way the difference in the titration curves of fibrinogen and of polymerized (clotted) fibrin. By subtracting from this difference the difference described above between fibrinogen and... 

Thrombotic Response to Protein-Coated Surfaces. Overview. Although Figures 2, 3, 5, 6, and 8-11 show fibrin(ogen) and platelet responses to many different surfaces, all of the curves have a similar appearance. At the first datum of 2 min, an initial amount of deposition was gener-... 

Fibrin zymograms may be subjected to densitometric analysis to obtain quantitative information about PA activity (Fig. 3). As can be seen, good calibration curves were obtained for both uPA and tPA over an approximately... 

Fig. 2. Fibrin zymography of PA standards. (A) Fibrin zymogram demonstrating electrophoretic migration of uPA (45-kDa), tPA (70-kDa), and higher molecular weight tPA/PAI-1 complex (110-kDa). Fibrin indicator gels were stained with amido black (see Section 3.5). Samples 1-5 correspond to PAs and PAIs of various compositions as described (R4, R5). (B) Calibration curve obtained with PA standards. Linear regression analysis was performed and correlation coefficient (r) is shown (r = 1.000, perfect correlation).

FIGURE 11 Kinetics curves of growth of Rayleigh light scattering intensity in the process of fibrin gel formation in the presence of Tl-MNP-0 (7), Tl-MNP-l (2) and Tl-0-0 (3). 

Fig. 41.4 The effects of a local application of TGF-beta and EGF on structural properties of the femur-graft-tibia complex after ACL reconstraction. The load-elongation curves of the femur-graft-tibia complexes in the knees with growth factor (GF) application, with fibrin sealant alone (sham), and without growth factor or fibrin sealant (control) groups and the normal femur-ACL-tibia complex (normal ACL). A combined application of TGF-betal and EGF significantly improved mechanical strength of the femur-graft-tibia complex at 12 weeks after ACL reconstruction (From Ref. [43]))...

Fig. 87. Changes in bound hydrogen ions occurring during the polymerization of fibrin monomer, obtained from Fig. 80 by subtracting the dashed curve from the solid curve (Mihalyi, 1954). The pK s shown were originally obtained by Mihalyi, on the basis of a calculation which is equivalent to assuming Ki, = . For an alternative interpretation see text.

Figure 2.16 Stress-strain curves of BC, bovine coronary artery reference (BV), untreated and treated glutaraldehyde BC/fibrin nanocomposites. Reproduced with permission from [133].

Mechanical Properties. Water-equilibrated fibrin film can be stretched to two to three times its initial length, and, unless held for some time in the stretched state, returns to its original shape when the load is removed. The response to stress is not as rapid as in true rubberlike materials, and the film undergoes slow creep under constant load, as well as slow creep recovery after removal of load. Furthermore, stress-strain curves over cycles of elongation and contraction exhibit marked hysteresis. 

Fia. 33. Stress-strain curves of water-plastioized fibrin film. Fibrin contents 1, 30% 2, 44% 3, 69%. From Ferry and Morrison (1947b). 

Properties of Steam-Treated Film, The properties of film treated with saturated steam at 121 for 20 minutes, the moisture content during treatment being 25%, have been examined in more detail. Compared with unmodified film, it has a lower affinity for water, as evidenced by its high water-equilibrated fibrin content of 57 %, as well as lower water sorption at different relative humidities. Several properties of the water-equilibrated film are directly attributable to its high fibrin content. Thus its opacity is quite low (optical density per mm. of 0.1 to 0.2, compared with 3.0 for water-equilibrated unmodified film) but unmodified film at the same fibrin content (Fig. 32) has a comparable opacity (0.5). Also, the stress-strain curve shows a high initial slope, the mechanical character being tough rather than rubbery it closely resembles the curve for unmodified film at the same fibrin content. 

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