<p> The fibrinolytic system has an important role in maintaining vascular patency by restricting fibrin clot formation to prevent occlusion of the blood vessel. Plasminogen activation is the central event in fibrinolysis and is tightly regulated by activators and inhibitors. Histidine-rich glycoprotein (HRG) is an abundant plasma protein that has been proposed to have a regulatory role in many biological processes, including fibrinolysis. Approximately 50% ofplasminogen in the blood circulates in complex with HRG. Conflicting reports dispute the role of HRG in fibrinolysis, specifically whether it promotes or inhibits plasminogen activation. To elucidate the role of HRG in fibrinolysis, we isolated HRG from human plasma and analyzed its effect on plasminogen activation by tissue-type plasminogen activator in a kinetic assay. HRG had no significant effect on plasminogen activation by tissue-type plasminogen activator once contaminating plasminogen was eliminated from our HRG preparations. Based on these results, the focus of our research was redirected to analyzing the effect of HRG on additional plasminogen activators, namely urinary-type plasminogen activator and factor (F) Xlla. HRG inhibited plasminogen activation by both activators. HRG had the greatest inhibitory effect on FXIIa activity. This novel finding led us to explore the relationship between HRG and FX.IIa by measuring the affinity of HRG for FXIIa by surface plasmon resonance, and by analyzing the effect of HRG on FXIIa activity in various contact pathway reactions. ZnCh was also included in these reactions because it plays an important role in enhancing both HRG-and FXII-mediated interactions and is released by activated platelets. In the presence of 12.5 μM ZnCl2, FXIIa bound to the histidine-rich region of HRG with very high affinity (Kd = 56 ± 8.9 pM). Interestingly, HRG does not bind to FXII. Functional analysis of HRG revealed that it significantly inhibits a number of contact pathway reactions, including FXII autoactivation, kallikreinmediated FXII activation, and FXIIa-mediated FXI activation. Conversely, HRG enhanced FXIIa-mediated prekallikrein activation. Based on these findings, we hypothesize that HRG binds to an exosite on FXIIa, which is not expressed by the zymogen FXII, and alters FXIIa activity. The mechanism of HRG-mediated FXIIa inhibition is not fully understood and needs to be further analyzed by both binding and functional assays. These observations raise the possibility that the main function of HRG is to modulate FXIIa activity, rather than plasminogen activation. Because of its abundance, HRG may function as a modulator of haemostasis through its effect on coagulation and fibrinolysis. </p> / Thesis / Master of Science (MSc)

Background: Advance in cardiac intervention improved the survival of patients with congenital heart diseases (CHD). However, they may have propensity of thromboembolism and the use of antithrombotic agents was generally based on small studies and consensus opinion. Objective: To systematically review the current literature on the efficacy and safety of various antithrombotic agents in patients with CHD. Methods: Studies published in English during the period 1990 – 2012 were identified using keyword search from PubMed, Medline, EMBase, and Cochrane Library. Additional search from reference sections of the articles and clinical trial registry was performed. Data extracted included: type of studies, number of patients, follow-up period during which the patients were on the antithrombotic agents, number of thromboembolic (TE) events, and all, major and minor bleeding events. Event rate as the proportion of events of the patients and event per 100 patients-year were obtained for respective antithrombotic agent in each study. Composite event rate and event per 100 patients-year were estimated after weighting. Results: Forty studies consisted of 5144 patients were reviewed. Observation period of 8916.6 years was available in 25 studies. Diagnostic categories included: Fontan operation 15, systemic-to-pulmonary artery shunt 7, mechanical valve 8, atrial septal defect occlusion device 2, cyanotic heart 1, mixed 7. Antithrombotic prophylaxis was not used in 13 studies, warfarin in 26, aspirin alone in 22, combined aspirin and dipyridamole in 2. Clopidogrel with concomitant antithrombotic agents was reported in 5 studies. Overall composite TE event rate was 3.9% (95% CI 2.3 – 5.4%) and that of all bleeding rate was 2.8% (95% CI 0 – 5.5%), with 1.4% (95% CI 0.0 – 2.6%) for major and 2.2% (95% CI 0.0 – 4.3%) for minor bleeding. Composite TE rate for no prophylaxis (9.6%; 05% CI 3.7 – 15.5%) was significantly greater than that of warfarin (1.7%; 95% CI 0.1 – 3.3%) and aspirin (1.3%; 95% CI 0.0 – 3.0%). Both TE and all bleeding rate showed no difference between warfarin and aspirin, while major bleeding tended to be higher in warfarin than aspirin(0.9% vs 0.0%, p=0.06). Fontan patients had overall TE rate of 2.7% (95% CI 0.1 – 5.4%). Patients with no prophylaxis (10.2%; 95% CI 9.2 – 18%) had significantly greater TE rate than warfarin (1.4%; 95% CI 0.0 – 0.4%) or aspirin (1.2%; 95% CI 0.0 – 3.0%). All bleeding rate in Fontan patients was 0.5% (95% CI 0.0 – 4.3%). Both TE ad bleeding rates showed no difference between warfarin and aspirin. Overall TE rate for shunt was 7.2% (95% CI 3.7 – 14.3%), being similar between aspirin group and no antithrombotic group. Patients with mechanical valves had TE rate of 7.3% (95% CI 2.9 – 11.6%) and all bleeding rate of 7.2% (95% CI 4.2 – 10.2%). There was no statistical difference between warfarin and APA group. Patients with ASD occlusion device has TE rate of 0.1% (95% CI 0.0 – 0.2%). No bleeding event was reported in the studies. Conclusion: Patients with congenital heart diseases were at risk of developing thromboembolism which justified the use of anti-thrombotic prophylaxis. Further studies relating the thromboembolic risk profile of patients with CHD to the efficacy of anti-thrombotic agents might help in selection of anti-thrombotic agents. / published_or_final_version / Community Medicine / Master / Master of Public Health

Diss. (sammanfattning) Uppsala : Univ., 2005. / Härtill 4 uppsatser.

Diss. (sammanfattning)--Stockholm : Karol. inst., 2002. / Härtill 5 uppsatser.

Statins are 3-hydroxy, 3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors, which block the cholesterol biosynthetic pathway to lower total serum levels and LDL-cholesterol. The cholesterol pathway also provides a supply of isoprenoids (farnesyl and geranylgeranyl) for the prenylation of signaling molecules, which include the families of Ras and Rho small GTPases. Prenyl groups provide a membrane anchor that is essential for the correct membrane localisation and function of these proteins. Statins deplete cells of lipid geranylgeranyl diphosphate (GGPP) thereby inhibiting progression of the mevalonate pathway and prenylation of proteins. Two such proteins are Rab27b and Rap1, small GTPase proteins that are involved in the secretion of platelet granule and integrin activation. We hypothesise that statins can impair prenylation of Rab27b and Rap1a in platelets and thereby attenuate platelet function. The specific aims of the project were to analyse the impact of statins on the prenylation status of Rab27b and Rap1a in platelets. As Rab27b and Rap1a are known to be involved in secretion of platelet granules a secondary aim was to analyse the downstream effects of statins on this process following activation. Finally, we assessed the impact of treatment of platelets with statins on thrombus formation, stability and resistance to fibrinolysis. Platelets incubated with statins overnight were separated into cytosolic (aqueous) and membrane (detergent) components and visualised by Western blot. An accumulation of Rab27b and Rap1a was observed in the cytosolic compartments of statins treated platelets compared to untreated platelets, thus indicating indirect evidence that statins attenuate prenylation of Rab27b and Rap1a in platelets. The most effective statin in attenuating prenylation of Rab27b and Rap1a was atorvastatin (ATV). The inhibitory effect of statins on prenylation was recovered by GGPP, indicating that the mechanism of inhibition involved the mevalonate pathway. Release of ADP from platelet dense granules was significantly impeded following overnight treatment with ATV. In line with the inhibition of prenylation of Rab27b and Rap1a by ATV, addition of GGPP rescued the release of ADP from platelet dense granules. This suggests that attenuation of dense granules release by ATV occurs via interference in the mevalonate pathway and the inhibition of Rab27b prenylation. Furthermore, ATV significantly attenuates α-granules release in thrombin stimulated platelets, which was visualised as impaired accumulation of endogenous P-selectin, PAI-1 and fibrinogen on the activated membrane. Changes in the activation of α₁₁bβ₃ integrin on the stimulated platelet surface, observed as defective binding of exogenous fibrinogen and PAC-1, were also evident following treatment of platelets with ATV. In addition, ATV treatment of platelets reduced binding of CD41a, indicating that the copy number and activation of α₁₁bβ₃ integrin on stimulated platelets was significantly reduced. Statins were also found to significantly inhibit thrombin-induced platelet aggregation following incubation of platelets overnight with therapeutic concentrations of statins. Surprisingly GGPP did not rescue platelet aggregation indicating that different mechanisms are involved in inhibition of platelet responses by statins. Incubation of whole blood with ATV overnight significantly altered several haemostatic parameters. Using thromboelastography we demonstrated a delay in the coagulation time and clot formation time. Maximum clot firmness was also significantly reduced in the presence of statins compared to the control. The effect on clot firmness generally arises from platelet dysfunction and/or a change in fibrinogen concentration and function; the latter was ruled out using a Fibtem test, which shows no difference between treated and untreated whole blood. Similarly, formation of platelet-rich plasma clots was significantly delayed following pre-treatment with ATV overnight. These clots also exhibited lower maximal absorbances, which could represent differences in the fibrin network structure. In line with the reduction in fibrinogen binding defective clot retraction was also observed in platelet-rich plasma pre-treated with ATV overnight. Similar clot retraction results were observed with tirofiban and CytoD, suggesting that the inhibitory effect of ATV may involve modulation of α₁₁bβ₃ integrin activation. Platelet-rich plasma clots formed post-treatment with statins were visualised by confocal microscopy and revealed significant alterations in clot structure; observed as thinner fibrin fibres and fewer platelet aggregates. Additionally, we demonstrated that statins modulate clot stability and shorten time to lysis. Clots formed from platelet rich plasma that was subjected to incubation with ATV overnight revealed faster lysis by tPA compared to the absence of statin. These findings are also in agreement with the lysis of Chandler model thrombi formed from overnight incubated whole blood with ATV, which demonstrated faster lysis rate mediated by tPA. Furthermore, statins were shown to change the clot thrombodynamics as assessed by HemaCore analyser, which shows that stains implicate both clot growth in response to TF-coated comb and spontaneous clot lysis by tPA. In conclusion, statins directly inhibit Rab27b and Rap1a prenylation in platelets and down-regulated dense granules release. Inhibition of Rab27b and Rap1a prenylation, and dense granules release was recovered by GGPP, indicating that these effects are mediated through the mevalonate pathway. Impairment of platelet aggregation by statins resulted via multiple mechanisms as GGPP did not recovered the inhibition of aggregation by ATV. Statins also modulate fibrinogen binding, α-granules release, clot retraction and clot formation and stability in vitro. Together these results suggest that statins may directly attenuate the platelet response in vivo. The pleotropic effect of statins on platelets may contribute to the protective function of these class of drugs in cardiovascular diseases.

Thesis (Ph.D.). / Written for the Dept. of Epidemiology, Biostatistics and Occupational Health. Title from title page of PDF (viewed 2008/07/23). Includes bibliographical references.

This study was aimed at investigating adverse and beneficial long-term effects of jejunoileal bypass (JIB) sugery in obese patients. The JIB was the first widly used surgical procedure for treatment of morbid obesity. The weight loss was remarkable, but the procedure was declared not appropiate for obesity surgery in the late 1970's. Serious late adverse effects such as liver cirrhosis and malignancies, have been postulated. Unexpectedly few studies have adressed these problems. In the long-term follow-up of 87 uniformly operated patients, several persisting beneficial effects were found. The mean Body Mass Index was 41.5 kg/m2 at the time of operation and 29.7 kg/m2 sixteen years after the operation. Diabetes type II and hyperlipidemia, common in an obese population, was not found in this group. Reversals were performed in 3% of the patients in contrast to 20-30% in many earlier studies. Revisions performed in 8% of the patients due to excessive weight loss could have contributed to the good long-term outcome. Percutaneous liver biopsies from 44 patients taken 14-20 (mean 17) years after JIB revealed normal or fatty liver, a lower degree of histological abnormalities than in 11 biopsies taken at the time of operations 1-14 (mean 6) years postoperatively. Liver cirrhosis seen early in one patient could not be found in the late biopsies. Reduced activity of the fibrinolytic system has been shown to be a new cardiovacular risk factor. In 45 patients studied 14-20 years after JIB, the levels of both plasminogen activator inhibitor type 1 (PAI-1) and tissue plasminogen activator (tPA) were significantly lower than in a control group of 10 morbidly obese patients ( PAI-1: 8.4 vs 32 U/mL, tPA: 7.2 vs 12 pg/L). Bile acids are regarded as cofactors in the carcinogenesis in the colon and experimentally an increased frequency of malignant tumors has been demonstated after JIB in carcinogen-induced rats. In 30 of the operated patients, colonoscopy with biopsy was performed 11-17 yeras after the operation. No evidence for malignant transformation was found as reflected by an abscense of polyp formation, histologic dysplasia or aneuploidia in flow cytometric DNA analysis. Eight hundred and thirty patients from 10 hospitals subjected to JIB were compared to 1660 controls with respect to malignant diagnosis over a 20 years period. No significantly increased risk for colorectal carcinoma could be demonstrated. However the overall risk for malignant disease was increased in the operated patients. The frequency of endometrial carcinoma was significantly elevated up to five years after the operation but was normal after that time. In conclusion the postulated progress of serious adverse effects of JIB such as liver cirrhosis and malignant disease has not been possible to demonstrate. Several beneficial effects such as weight loss and reduction of cardiovascular risk factors have been found a long time after the operation. / <p>Diss. (sammanfattning) Umeå : Umeå universitet, 1995, härtill 5 uppsatser.</p> / digitalisering@umu

Diss. (sammanfattning) Uppsala : Univ., 2002. / Härtill 4 uppsatser.

Thesis (Ph. D.)--Michigan State University, 2005. / Includes bibliographical references (leaves 51-64). Also available online (PDF file) by a subscription to the set or by purchasing the individual file.

Thesis (Ph. D.)--Chemical Engineering, Georgia Institute of Technology, 2006. / Chaikof, Elliot, Committee Chair ; Hanson, Stephen, Committee Member ; Lollar, John "Pete", Committee Member ; Sambanis, Athanassios, Committee Member ; Yoganathan, Ajit, Committee Member.