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The Effects of Shear Stress and L- arginine on Platelet Activation and Adhesion

The Effects of Shear Stress and L- arginine on Platelet Activation and Adhesion. Jeffrey Fontenot, REU Student. The Purpose of Platelets. To seal off any broken or leaking blood vessels Protecting damaged tissue while it heals.

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The Effects of Shear Stress and L- arginine on Platelet Activation and Adhesion

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  1. The Effects of Shear Stress and L-arginine on Platelet Activation and Adhesion Jeffrey Fontenot, REU Student

  2. The Purpose of Platelets • To seal off any broken or leaking blood vessels • Protecting damaged tissue while it heals http://biomed.brown.edu/Courses/BI108/BI108_2005_Groups/10/webpages/plateletslink.htm

  3. Problems with Platelets • Under-activity • Clots do not form when needed • Excessive bleeding • Wounds not healing quickly or properly • Over-activity • Clots and thrombi form in unnecessary places or situations • Thrombi may become larger than needed • Heart attack and stroke may result

  4. Goals • The end goal • Develop processes and devices that can measure platelet activity • Diagnose platelet problems or dysfunction in the clinical setting • Intermediate goal • Show that L-arginine decreases platelet adhesion • Show that higher shear stress will increase platelet adhesion

  5. The Experiment • New work • Use different shear stresses ranging from 1 to 15 dynes/cm2 • Use two different concentrations of L-arginine, 0 and 20 µM/L • Reproducing previous results • Positive control • Constant flow rate • Change L-arginine concentrations from 0 to 25 µM/L

  6. Setup • Cut out micro channels • Layer-by-Layer self assembly • Manifold and syringe pump • Calculate flow rate from the desired shear stress • Bovine blood is collected and spun down to separate the Platelet Rich Plasma (PRP) which settles on the top

  7. The Experiment PRP travels down through the channel for one minute. The channels are rinsed with PBS Each channel is dyed with acridine orange

  8. Processing • Each channel is photographed 22 times • The images are processed through a MatLab code • The average percent coverage is calculated in Excel

  9. Results The positive control results

  10. Results The current work results

  11. What does this Mean? • Shear stress and L-arginine do have effects on platelet adhesion • Increasing shear stress appears to decrease adhesion • Possibly due to sodium citrate, Yasuo et al. • Source of errors

  12. Conclusion • Correct the errors • The results appear to be opposite of the expected • There are more factors than originally expected • The anticoagulant may play a role • Is there a delay between activation and adhesion • Is the thrombus forming and breaking up

  13. Acknowledgements Dr. Steven Jones Melanie Groan Louisiana Tech University National Science Foundation

  14. Questions?

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