published_or_final_version / abstract / Medicine / Doctoral / Doctor of Philosophy

Fibrinolysis is the process by which fibrin blood clots are dissolved. Fibrinolytic research is clinically relevant because decreased fibrinolytic potential is linked to increased risk of an ischemic event. Fibrinolysis is known to increase in response to aerobic exercise, however, few research studies have focused on the fibrinolytic response to resistance exercise. Furthermore, women are severely underrepresented in fibrinolytic research, and there are no current studies that focus on women and resistance exercise. Estrogen has been shown to affect basal fibrinolytic potential resulting in the need for fibrinolytic research focused on female subjects. Body composition is known to influence basal fibrinolysis leaving individuals with higher absolute amounts of body fat at risk for cardiovascular events due to decreased fibrinolytic potential. Little is known, however, about the influence of body composition on the fibrinolytic response to exercise. Purpose. The purpose of this study was to describe the fibrinolytic response to acute resistance training in young women, and further, to determine how body fat percentage affects fibrinolysis at rest and following resistance exercise. Methods. Twenty-three sedentary, healthy women (22.5 ± 4 yrs, 22.3 ± 3.0 kg•m 2) participated in the study. Body fat percentage and fat distribution were assessed using dual-energy X-ray absorptiometry (DEXA), and subjects were separated into two groups by body fat percentage: <30% (lean, n=12) and >30% (obese, n=11). Each subject performed 6 sets of 10 leg extension repetitions at an intensity associated with 70% of her one-repetition maximum. The two primary mediators of fibrinolytic potential, tissue plasminogen activator (tPA) and plasminogen activator inhibitor 1(PAI-1), were assessed at baseline and immediately after exercise in venous blood. Results. tPA activity increased in response to acute resistance exercise (p<0.05), however, there was no significant change in PAI-1 activity (p>0.05). A significant main effect of group was observed, indicating the lean women had higher tPA activity (p<0.05) and lower PAI-1 activity (p<0.05) than the obese group. A significant time x group interaction indicated that the tPA response was blunted in the obese group (p<0.05). Conclusions. Fibrinolytic potential increases in response to acute resistance exercise in young women due to increases in tPA activity. Obese women demonstrate a decreased fibrinolytic potential at rest and following acute resistance exercise compared to lean women. Given the relationship between fibrinolytic potential and outcomes of cardiovascular disease, these physiological responses suggest that overweight women may be at elevated risk of an adverse cardiovascular event both at rest and during exercise. / School of Physical Education, Sport, and Exercise Science

Cell therapy, including human mesenchymal stem cell (hMSC) therapy, has the potential to treat different pathologies, including myocardial infarctions (heart attacks). Biological sutures composed of fibrin have been shown to effectively deliver hMSCs to infarcted hearts. However, hMSCs rapidly degrade fibrin making cell seeding and delivery time sensitive. To delay the degradation process, we propose using aprotinin, a proteolytic enzyme inhibitor that has been shown to slow fibrinolysis. This project investigated the effects of aprotinin on hMSCs and suture integrity. Viability of hMSCs incubated with aprotinin, examined using a LIVE/DEAD stain, was similar to controls. No differences in proliferation, as determined by Ki-67 presence, and were observed. hMSCs incubated in aprotinin differentiated into adipocytes, osteocytes, and chondrocytes, confirming multipotency. CyQuant assays were used to determine the number of cells adhered to fibrin sutures. The number of adhered cells was increased through aprotinin supplementation at Days 2, 3, and 5 time points. To examine the effect of aprotinin on suture integrity, sutures were loaded to failure to determine ultimate tensile strength (UTS) and modulus (E). Sutures exposed to aprotinin had higher UTS and E when compared to sutures exposed to standard growth media. Degradation of fibrin was quantified using an ELISA to quantify fibrin degradation products (FDP) and by measuring suture diameter. Fibrin sutures incubated in aprotinin had larger diameters and less FDP compared to the controls, confirming decreased fibrinolysis. These data suggest that aprotinin can reduce degradation of biological sutures, providing a novel method for extending the implantation window and increasing the number of cells delivered for hMSC seeded biological sutures.

Elevated plasma concentrations of lipoprotein(a) (Lp(a)) are associated with increased risk of atherothrombotic disease. Lp(a) is a unique lipoprotein consisting of a low density lipoprotein-like moiety covalently linked to apolipoprotein(a) (apo(a)), a homologue of the fibrinolytic proenzyme plasminogen. Apo(a) is extremely heterogeneous in size with small isoforms being independently associated with increased cardiovascular risk. Several in vitro and in vivo studies have shown that Lp(a)/apo(a) can inhibit tissue-type plasminogen activator (tPA)-mediated plasminogen activation on fibrin surfaces, although the mechanism of inhibition by apo(a) remains controversial. Essential to fibrin clot lysis are a number of plasmin-dependent positive feedback reactions that enhance the efficiency of plasminogen activation, including the plasmin-mediated conversion of Glu1-plasminogen to Lys78-plasminogen. Additionally, abnormal fibrin clot structures have been associated with both an increased risk of cardiovascular disease and elevated Lp(a) levels. Similarly, oxidized phospholipids have been implicated in the development of cardiovascular disease, and are not only preferentially carried by Lp(a) in the plasma but have also been shown to covalently-modify both apo(a) and plasminogen. In this thesis, we built upon the understanding of the role of apo(a) in plasminogen activation on the fibrin/degraded fibrin surface by determining that: (i) apo(a) inhibits plasmin-mediated Glu1-plasminogen to Lys78-plasminogen conversion and identifying the critical domains in apo(a) responsible for this effect, (ii) apo(a) isoform size does not affect either the inhibition of tPA-mediated plasminogen activation or the inhibition of plasmin-mediated Glu1-plasminogen to Lys78-plasminogen conversion, (iii) apo(a) modifies fibrin clot structure to form more dense clots with thinner fibers and reduced permeability, modifications that enhance the ability of apo(a) to inhibit tPA-mediated plasminogen activation and (iv) the phosphorus content of apo(a) affects its ability to inhibit tPA-mediated plasminogen activation and the phosphorus content of plasminogen affects its ability to be activated by tPA. By understanding these individual reactions, each of which has the potential to affect the broader fibrin clot lysis process, we have expanded our understanding of the overall effect of Lp(a)/apo(a) in the inhibition of plasminogen activation on the fibrin/degraded fibrin surface and thus broadened our understanding of how Lp(a)/apo(a) may mediate the inhibition of thrombolysis in vivo. / Thesis (Ph.D, Biochemistry) -- Queen's University, 2011-12-14 08:26:54.99

The purpose of this study was to examine the fibrinolytic response to whole body vibration (WBV) and exercise in men. Methods. Twenty healthy males (23.8 ± 4.2 years, 80.8 ± 3.3 kg·mˉ²) participated in the study. Each subject performed 3 trials in randomized order separated by 1 week. The trials consisted of exercise (X), vibration (V) and vibration + exercise (VX). Exercise sessions consisted of 15 minutes of unloaded squatting at a rate of 20 per minute. Vibration sessions were conducted on a WBV platform vibrating at a frequency of 30 Hz and amplitude of 1.5mm for 15 minutes. Plasma concentrations of active tPA and PAI-1 samples were assessed at baseline and immediately after each session. Results. tPA activity change from pre to post trial was found to be significantly greater in the VX condition (0.87 ± 0.35 IU·mlˉ¹ to 3.21 ± 1.06 IU·mlˉ¹) compared to the X (0.71 ± 0.36 IU·mlˉ¹ to 2.37 ± 1.13 IU·mlˉ¹) or V (0.83 ±0.25 IU·mlˉ¹ to 1.00 ± 0.37 IU·mlˉ¹) condition. tPA activity change from pre to post trial was found to be significantly greater in the X condition compared to the V condition. PAI-1 activity change from pre to post trial was found to be significantly decreased in the VX (6.54 ± 5.53 IU·mlˉ¹ to 4.89 ± 4.13 IU·mlˉ¹) and X (9.76 ± 8.19 IU·mlˉ¹ to 7.48 ± 7.11 IU·mlˉ¹) conditions compared to the V (5.68 ± 3.53 IU·mlˉ¹ to 5.84 ± 3.52 IU·mlˉ¹) condition. Heart rate change from pre to post exercise for the V condition (pre, 75 ± 8 bpm; post, 90 ± 7 bpm) was less than the change in the VX condition (pre, 77 ± 13 bpm; post, 148 ± 19 bpm) and X condition (pre, 71± 11 bpm; post, 139 ± 22 bpm). The change in heart rate was found to be similar in the X and VX conditions. Peak RPE was not significantly different between X and VX sessions. Conclusions. WBV does not stimulate increased fibrinolytic activity in young men. However, the significant increase in fibrinolytic potential observed during squatting exercise is enhanced by concurrent WBV. / School of Physical Education, Sport, and Exercise Science

Access to abstract permanently restricted to Ball State community only / Access to thesis permanently restricted to Ball State community only / School of Physical Education, Sport, and Exercise Science

Thesis (Ph. D.)--University of Hong Kong, 2007. / Also available in print.

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2005. / Härtill 4 uppsatser.

Thesis (Ph.D. in Clinical Science) -- University of Colorado Denver, 2008. / Typescript. Includes bibliographical references (leaves 136-146). Free to UCD Anschutz Medical Campus. Online version available via ProQuest Digital Dissertations;

Thesis (doctoral)--Karolinska Institutet, Stockholm, 1991. / T.p. with thesis statement inserted. Includes bibliographical references.