Assessments of thrombogenicity by three in vitro techniques. Student Research Award in the Undergraduate, Master Candidate, or Health Science Degree Candidate Category, 21st annual meeting of the Society for Biomaterials, San Francisco, CA, March 18-22, 1995.

This study assessed three in vitro techniques designed to measure the thrombogenicity of vascular grafts. All techniques immersed vascular grafts in rotating blood. In the gravimetric analysis, the weight of adherent thrombi was recorded at 2 min intervals for 20 min. In the torque analysis, a microviscometer continuously recorded the amount of torque developed as the graft rotated for 20 min. In the thrombin analysis, the blood sample was analyzed for fibrinopeptide A production indicating fibrinogen cleavage. Expanded polytetrafluoroethylene grafts were treated by removal of air nuclei (denucleation), binding of heparin, or binding of polyethylene oxide (PEO). The gravimetric analysis determined that the time at which each group experienced clot initiation was as follows: control after 6 min, denucleation after 14 min, heparin after 18 min, and PEO after 10 min. Similarly, in the torque analysis all treatment groups significantly delayed the initial increase in torque from 8.0 min for control to 12.5 min for denucleation (P < .01), > 20 min for heparin (P < .01), and 12 min for PEO (p < .05). The thrombin analysis determined that coagulation activity was reduced relative to control at 12 min with the denucleation group (P < .05) and heparin group (P < .01) and at 18 min with all treatment groups (P < .01). The similarity of results among the techniques increases confidence that each measurement accurately predicts in vitro thrombogenicity.

Altered distribution of mitochondria and actin fibers in 3T3 cells cultured on microcarriers.

The mitochondria and actin fibers of 3T3 fibroblasts cultured on microcarriers in spinner flasks were visualized using fluorescent stains. In contrast to cells grown on planar surfaces under static or steady laminar flow conditions, cells exposed to higher levels of turbulent agitation do not form actin stress fibers. Greater agitation also leads to a more diffuse appearance of the mitochondria and a wider distribution of them throughout the cytoplasm. This response may indicate damaged mitochondria, as similar results have been reported for chemical toxins.