Background: Surgical hemostasis is achieved using adjunctive hemostats when conventional methods fail.Objective:This study compares the effectiveness of two adjunctive gelatin-thrombin hemostats.Hypothesis:To determine effectiveness, hemostats were compared in vivo, in vitro, and using scanning electron microscopy (SEM).Methods:In vivo, a heparinized porcine liver abrasion model was used to compare hemostatic success, degree of bleeding, and blood loss at 2, 5, and 10 minutes post-treatment. In vitro, thrombin in the supernatant of each hemostat and Red Blood Cells (RBC'S) in the supernatant of clots formed by each was compared.Results:Ultrastructure of one gelatin was smooth and the other stellate. In vivo, smooth gelatin provided superior hemostatic success at 5 (85% vs. 60%; OR: 5.3; 95% CI: 1.66 to 17.9) and 10 mins (72.5% vs. 47.5%; OR: 5.0; 95% CI: 1.55 to 16.1). Smooth gelatin had a statistically different degree of bleeding at 5 (0.58 ± 0.87 [Mean ± SD] vs. 1.03 ± 1.12; OR: 3.36; 95% CI: 1.34 to 8.41) and 10 mins (1.13 ± 1.14 vs. 1.65 ± 1.05; OR: 3.87; 95% CI: 1.62 to 9.21). Mean blood loss was less with smooth gelatin at 2 (0.07 ± 0.19 vs. 0.13 ± 0.63 ml/min), 5 (0.04 ± 0.13 vs. 0.23 ± 0.45 ml/min), and 10 mins (0.09 ± 0.24 vs. 0.21 ± 0.32 ml/min). In vitro, supernatant of smooth gelatin had significantly less thrombin (6.81 vs. 10.9 IU/ml, p = .001), and significantly less RBC's than stellate gelatin (0.07 vs. 0.09 × 106/ul, p = .0085).Conclusion:Smooth gelatin has an increased ability to retain thrombin and RBC's in vitro which may explain why it provides superior hemostatic effectiveness, superior control of bleeding, and greater reduced blood loss in vivo.

This study analyzed the ability of fibrin gels to deliver added recombinant transforming growth factor beta-1 (TGF-beta1) in a controlled manner and biologically active form. First, the effects of the amount of TGF-beta1 on the release kinetics were analyzed using a single fibrin gel formulation (fibrinogen complex (FC) at 25 mg/mL, thrombin at 2 IU/mL). Then, the effects of FC and thrombin concentrations were analyzed. Finally, to test the biological activity of the released TGF-beta1 from the gels, medium supernatants taken from gels at day 3 were used as culture medium for human mesenchymal stem cell (HMSC) monolayers. Cell proliferation was analyzed after staining with calcein dye, and changes in cell morphology were observed under fluorescence microscopy at days 1, 4, and 7. At day 7, HMSC chondrogenic differentiation was assessed by Alcian Blue staining and osteogenic differentiation by alkaline phosphatase activity and Alizarin Red staining. Results showed that TGF-beta1 added to fibrin gels was gradually released from the gels and increased with the amount of TGF-beta1 initially seeded, with a total of approximately 50% of the initial amount released by day 10 (with gels containing 25 mg/mL of FC and 2 IU/mL of thrombin). The release was lower with increasing FC concentrations, suggesting a binding affinity of TGF-beta1 with the FC component. Varying the thrombin concentration had a lesser effect. HMSC monolayers cultured with medium supernatants collected from gels at day 3 and containing released TGF-beta1 showed a change in morphology (squared to polygonal), lower cell proliferation, positive Alcian Blue staining but low levels of osteogenic differentiation markers. These results demonstrated that released TGF-beta1 was still bioactive and tended to induce mainly chondrogenic differentiation of the HMSC. Overall, the present study demonstrated that fibrin gels could be used as a carrier matrix for controlled release of bioactive TGF-beta1 by adjusting the concentrations of FC and thrombin in the gels.

The common phenomenon of lightning still harbors many secrets and only recently a new propagation mode was observed for negative leaders. While propagating in this "intensely radiating negative leader" (IRNL) mode a negative leader emits 100 times more very-high frequency (VHF) and broadband radiation than a more normal negative leader. We have reported that this mode occurs soon after initiation of all lightning flashes we have mapped as well as sometimes long thereafter. Because of the profuse emission of VHF the leader structure is very difficult to image. In this work we report on measurements made with the LOFAR radio telescope, an instrument primarily built for radio-astronomy observations. For this reason, as part of the present work, we have refined our time resolved interferometric 3-dimensional (TRI-D) imaging to take into account the antenna function. The images from the TRI-D imager show that during an IRNL there is an ionization front with a diameter in excess of 500 m where strong corona bursts occur. This is very different from what is seen for a normal negative leader where the corona bursts happen at the tip, an area of typically 10 m in diameter. The observed massive ionization wave supports the idea that this mode is indicative of a dense charge pocket.

The following full text is a publisher's version.For additional information about this publication click this link. https://repository.ubn.ru.nl/handle/2066/289944Please be advised that this information was generated on 2024-05-30 and may be subject to change.

• Our new LOFAR imaging procedure can locate over 200 sources per millisecond of flash with meter-scale accuracy. • The Primary Initial Leader breaks up into many (more than 10) negative leaders of which only one or two continue after 30 ms. • Some negative leaders propagate from the positive charge layer back to get close to the initiation point.