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1
Seyer, Christian. "Funktionelle und proteinbiochemische Charakterisierung von Fibin." Doctoral thesis, Universitätsbibliothek Leipzig, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-109763.
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Im Zebrafisch (Danio rerio) ist ein Protein identifiziert worden, das eine wichtige Rolle in der Entwicklung der Brustflossen zu besitzen scheint und als Fibin, dem englischen Akronym für Fin bud initiation factor (Flossenknospeninitiationsfaktor), bezeichnet wurde. Es zeigt keine Verwandtschaft zu anderen bekannten Proteinen, enthält keine typischen Strukturmotive, wird auf nur einem Exon kodiert und ist in allen bisher untersuchten Vertebraten, einschließlich des Menschen, evolutionär hoch konserviert. Ziel der vorliegenden Arbeit war die nähere funktionelle und proteinbiochemische Charakterisierung Fibins. In vielen Geweben adulter Mäuse (Mus musculus), v. a. in zerebralen und muskulären Proben, konnte Fibin mRNA nachgewiesen werden. Im Vergleich zum Adultus war die Expression in Geweben pränataler Mäuse bedeutend höher und unterschied sich in der Region der Vordergliedmaßen kaum von der im Torso. In L929 (Fibroblasten) und HEK Zellen (embryonale Nierenzellen) wurde eine hohe Expression von Fibin nachgewiesen, die in L929 Zellen durch Glukokortikoide und Aktivatoren des Proteinkinase C / MAP-Kinase , Proteinkinase A sowie des NF-κB / AP-1 bzw. Nrf2 / ARE Signalwegs erhöht werden konnte. Die nicht-proteinkodierende 5‘ Region des humanen Fibin Gens zeigte im Luciferase Reporterassay in L929 und HEK Zellen promotogene Eigenschaften, mit einem Aktivitätsmaximum der Sequenz – 836 Basenpaare bezogen auf den Translationsstartpunkt. In L929 Zellen wurde die promotogene Aktivität durch Glukokortikoide und Aktivatoren des Proteinkinase C / MAP-Kinase- sowie des NF κB / AP 1 bzw. Nrf2 / ARE Signalwegs erhöht. Fibin besitzt eine putative N terminale Signalsequenz und eine N Glykosylierungsstelle, die beide experimentell bestätigt wurden. Rekombinantes Fibin zeigte in der Fluoreszenzmikroskopie in COS-7 Zellen (Fibroblasten) eine hohe Kolokalisation mit dem Endoplasmatischen Retikulum, jedoch nur eine geringe mit dem Golgi Apparat. In COS-7 Zellen wurde es nicht über den sekretorischen Weg freigesetzt und zeigte in proteinbiochemischen Untersuchungen eine hohe Tendenz zur Aggregation und Ausbildung von Disulfidbrücken. Es ist anzunehmen, dass Fibin möglicherweise ein bisher unbekanntes Protein für die Ausbildung von Heteromeren benötigt, um erfolgreich sezerniert zu werden.
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Seyer, Christian [Verfasser], Torsten [Akademischer Betreuer] Schöneberg, Joachim [Gutachter] Thiery, and Rolf [Gutachter] Gebhardt. "Funktionelle und proteinbiochemische Charakterisierung von Fibin / Christian Seyer ; Gutachter: Joachim Thiery, Rolf Gebhardt ; Betreuer: Torsten Schöneberg." Leipzig : Universitätsbibliothek Leipzig, 2013. http://d-nb.info/1238366287/34.
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若原, 隆史. "ゼブラフィッシュの胸びれ形成に関与する新規分泌性タンパク質fibinの役割." 京都大学 (Kyoto University), 2007. http://hdl.handle.net/2433/137128.
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Moreira, Marcos Mello. "Variaveis capnograficas e d-dimeros em pacientes com suspeita de tromboembolismo pulmonar." [s.n.], 2009. http://repositorio.unicamp.br/jspui/handle/REPOSIP/311721.
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Orientadores: Renato Giuseppe Giovanni Terzi, Ilma Aparecida PaschoalTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Ciencias Medicas
Made available in DSpace on 2018-08-12T22:30:15Z (GMT). No. of bitstreams: 1 Moreira_MarcosMello_D.pdf: 18313915 bytes, checksum: db1efb99a56b2256d14393f2e951147a (MD5) Previous issue date: 2009
Resumo: Métodos para confirmar o diagnóstico de tromboembolismo pulmonar (TEP) são relativamente invasivos, de alto custo e nem sempre disponíveis. Justifica-se a busca de métodos mais acessíveis, de baixo custo, minimamente invasivos e que possam ser realizados à beira do leito. Foi objetivo deste estudo estabelecer um protocolo de triagem diagnóstica de TEP, minimamente invasivo e de baixo custo, usando para isto a capnografia volumétrica (CV) e o Oímero-O (DO) (ELISA Rápido), para pacientes internados em diferentes unidades de um hospital terciário, atentanto para as possíveis limitações deste protocolo. Foi realizado um estudo prospectivo e observacional com 92 pacientes. Um estudo prévio de CV em 114 voluntários estabeleceu o padrão de normalidade para as variáveis analisadas. No grupo TEP, a CV foi associada à gasometria arterial para cálculo das variáveis do espaço morto e à dosagem do DO. O padrão-ouro para diagnóstico de TEP foi dado pela cintilografia de inalação/perfusão e/ou, tomografia computadorizada helicoidal e/ou, arteriografia pulmonar. Isoladamente, a variável capnográfica que apresentou melhor sensibilidade e especificidade foi a fração tardia do espaço morto alveolar (tO/ate) (91% e 98%, respectivamente). Obteve-se um resultado falso-negativo para o DO e, para a tO/ate, um falso-positivo e três falso-negativos. Quando a tO/ate ,foi associada ao DO, conseguiu-se 100% sensibilidade e 17% de especificidade. Uma outra variável capnográfica importante, por sugerir função pulmonar prévia anormal, e por esta razão, sinalizar uma possível limitação da tO/ate, foi o slope da fase III do capnograma. Por meio dos dados da CV de ambos os grupos (controle e doentes), estabeleceu-se um protocolo que ajuda a direcionar a equipe multiprofissionál quando da suspeita clínica de TEP.
Abstract :Background: Tests used to confirm a diagnosis of pulmonary embolism (PE) are relatively invasive, costly and not always available. Minimally invasive methods that are more accessible, less expensive and easily applied should be sought. Objective: To establish a low-cost, minimally invasive, PE diagnostic protocol in hospitalized patients, using capnographic variables and ELlSA D-dimer (DD) to rule out PE. Methods: A prospective observational study was conducted in 92 patients with suspected PE. The values of reference group for volumetric capnography (VCap) were used in order to compare with patterns of patients with PE. The patients were submitted to arterial blood gas analysis (to calculate the dead space variables) and had the DD values determined. The diagnosis was confirmed through ventilation/perfusion scintigraphy, spiral computed tomography, pulmonary arteriogram, or combinations of the three. Results: The capnographic variable that presented the greatest sensitivity and specificity (91 % and 98%, respectively) was the late dead space fraction (fDlate). Our findings include one false-negative DD result, as well as three false-positive and eight false-negative fDlate results. The combination of the fDlate and DD testing presented 100% sensitivity and 17% specificity. Another important capnographic variable, the phase 111 slope, indicated a possible limitation of VCap, since it interferes with the calculation of fDlate. Conclusion: The protocol established could guide multiprofessional teams in the management of clinical suspicion of PE. We were able to determine that the phase 111 slope might interfere with the calculation of fDlate, especially in patients with a history of abnormal lung function. Throught VCap variables (control group and sickness); was possible establishes a protocol that guide the multiprofissional team in cases of PE.
Doutorado
Pesquisa Experimental
Doutor em Cirurgia
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楠, 直樹. "分泌性因子SclerostinおよびFibinの骨形成における役割に関する研究." 京都大学 (Kyoto University), 2006. http://hdl.handle.net/2433/144286.
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Sathananthan, Saranya. "Modulating fibrin matrix properties via fibrin knob peptide functionalized microgels." Thesis, Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/44905.
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Fibrin is the body's natural provisional matrix activated in response to vascular injury in which noncovalent knob:hole interactions between fibrin monomers lead to the assembly of fibrin for clot formation. In this study we aimed to exploit fibrin knob:hole affinity interactions with swelling, space filling microgels for the development of a potential bio-synthetic hybrid polymer system with hemostatic properties. Previous work has explored the inherent binding interactions of various fibrin knobs and their complementary polymerization holes, which have led to the development of fibrin knob peptide mimic (GPRPFPAC) with enhanced binding affinity for fibrin(ogen) holes. By coupling this enhanced fibrinogen binding peptide with a pNIPAm microgel system capable of being dynamically tuned and self-assembled, we hypothesized the specific and rapidly triggered formation of a bulk hydrogel in a wound environment (i.e. in the presence of fibrinogen). We found that at the peptide ligand density and concentrations of microgels used, that a rapid formation of a gel did not occur in the presence of fibrinogen alone. However with fibrinogen and thrombin, we found that fibrin network polymerization, structure, and viscoelastic properties were greatly altered in the presence of knob peptide-conjugated microgels.
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Soon, Allyson Shook Ching. "Exploiting fibrin knob:hole interactions for the control of fibrin polymerization." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/45917.
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The minimization of blood loss represents a significant clinical need in the arena of surgery, trauma, and emergency response medicine. Fibrinogen is our body's native polymer system activated in response to tissue and vasculature injury, and forms the foundation of the most widely employed surgical sealant and hemostatic agent. Non-covalent knob:hole interactions are central to the assembly of fibrin that leads to network and clot formation. This project exploits these affinity interactions as a strategy to direct fibrin polymerization dynamics and network structure so as to develop a temperature-triggered polymerizing fibrin mixture for surgical applications.
Short peptides modeled after fibrin knob sequences have been shown to alter fibrin matrix structure by competing with native fibrin knobs for binding to the available holes on fibrinogen and fibrin. The fusion of such knob peptides to a non-native component should facilitate binding of the fused component to fibrinogen/fibrin, and may permit the concomitant modification of the fibrin matrix. We examined this hypothesis in a three-step approach involving (a) analyzing the ability of tetrapeptide knob sequences to confer fibrin(ogen) affinity on a non-fibrin protein, (b) investigating the effect of knob display architecture on fibrin(ogen) structure, and (c) designing a temperature-responsive knob-displaying construct to modulate fibrin(ogen) affinity at different temperature regimes, thus altering fibrin(ogen) structure.
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Allan, Peter. "Microrheology of fibrin clots." Thesis, University of Leeds, 2012. http://etheses.whiterose.ac.uk/3042/.
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An active particle tracking microrheology technique has been developed to study the viscoelastic properties of human fibrin and plasma clots. In order to perform microrheology measurements, a magnetic microrheometer device has been adapted and a technique developed, following the procedure of Evans et al., to measure the frequency dependent viscoelastic moduli (G() and G()). This technique has been supported by complementary investigation methodologies, such as protein analysis, turbidity, and multiple microscopy techniques. As a result of this study new insights into the viscoelastic dynamics of fibrin have been revealed. Three stress relaxation mechanisms, as predicted by Morse et al. for networks of semi-flexible fibres, were observed and occur on distinctly different timescales. The scaling of the tension dominated contribution was measured to scale as G ~ c2.7 0.2 in agreement with the prediction of Mackintosh. The presence of FXIII resulted in stiffer less deformable clots but was found to have no effect on the viscoelastic dynamics of clots. Frequency measurements of the loss tangent revealed that on timescales intermediate between stress relaxation modes clots were much more susceptible to permanent deformation. The effect of fibrinogen, thrombin and calcium on the viscoelastic behaviour of clots was also investigated. Increased fibrinogen levels produced clots which displayed predominantly elastic behaviour on shorter time-scales. The molecular mechanism underpinning the role of fibrinogen γ in fibrin clot polymerisation, structure and viscoelasticity was also investigated. We report new data which show that fibrinogen γ is associated with the formation of mechanically weaker, non-uniform clots composed of thinner fibres. This is caused by direct disruption of protofibril formation by and not through thrombin inhibition or binding to FXIII. In addition, the effects of the plasma proteins FVIIa, FIXa, FXIIa and FXIII on clot properties are also reported.
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Purves, Maud. "The D-domain of fibrin : structural and functional studies." Doctoral thesis, University of Cape Town, 1987. http://hdl.handle.net/11427/27202.
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The D-domain of fibrin (ogen) was separated from the parent molecule by plasmin digestion in the presence of calcium and isolated by means of DEAE-anion exchange chromatography followed by gel-filtration in buffer containing 4 M urea. Fluorescent-D-dimer (f-D-dimer) was isolated from a plasmic digest of fibrin clotted in the presence of 2.45 mM dansyl cadaverine, a fluorescent lysine analogue. Fluorescent-D-monomer was a by-product of f-D-dimer purification, the yield being determined by the concentration of dansyl cadaverine. At 2.45 mM f-D-monomer was always present in the digest. The f-D-monomer is probably formed directly and not as a result of degradation of f-D-dimer. The molecule elutes in the fibrinogen-derived-D- monomer position on gel-filtration. A protease was isolated and partially purified from venom of the puffadder (Bitis arietans). Puffadder venom protease is characterized by its ability to cleave D-dimer into symmetrical D-monomers, smaller than plasmin-derived D-monomers from fibrinogen. This characteristic was used to detect the puffadder venom protease activity with fluorescent-D-dimer being used as the substrate. Fractions obtained were assayed for D-dimer cleavage activity and the samples analyzed by means of SDS-PAGE on 4-20% gradient gels under reducing (βME) and non-reducing conditions. The fluorescent bands were located under U.V light and photographed prior to staining with Coomassie Blue. Several methods for the purification of the protease were investigated.
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Fatah, Kamaran Tahir. "Studies on fibrin gel structure /." Stockholm, 1998. http://diss.kib.ki.se/search/diss.se.cfm?19980608fata.
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Naidoo, Dhesigen P. "Metals and the conformation of fibrin." Master's thesis, University of Cape Town, 1992. http://hdl.handle.net/11427/26555.
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The carboxy terminal of the γ-chain of human fibrinogen contains at least three biologically. important functional domains: (i) the fibrinogen γ-chain polymerisation centre, (ii) the platelet receptor domain and (iii) the site for staphyloccocal clumping. The nature of the site specificity of these interactions necessitates the existence of a preferred conformation for this region, the nature of which has yet to be clearly established. A novel zinc metalloproteinase isolated from puff adder venom (PAV protease) capable of specifically cleaving the di-γ-chain of transglutaminase (Factor XIIIa) catalysed crosslinked plasmin derived D-dimer into apparently symmetrical monomers has been described. The activity is fibrin specific and displays an unusual site specificity for the γ-carboxy terminal domains within the crosslink region. The activity was reported to be potentiated by zinc. The effect of zinc on the digestion of D-dimer by PAV protease was evaluated by SDS-PAGE and by a fluorimetric technique utilising a fluorescent dansylcadaverine conjugate of the substrate (f-D-dimer). A differential zinc binding study determined that the potentiation of activity by zinc was due to a zinc-substrate rather than a zinc-enzyme interaction. The binding constant for zinc to D-dimer was determined by Scatchard analysis of zinc titration data. The interaction of zinc and f-D-dimer was confirmed by fluorescence anisotropy determinations. The nature of the coordination capsule around the metal cation was determined by examining a cobalt-fibrin-D-dimer complex and characterising the difference visible absorption spectrum thereof. The donor ligands from the D-dimer fragment for the metal ion were determined as histidines by examining zinc(II) and cobalt(II) binding to diethylpyrocarbonate modified fibrin-D-dimer and hydroxylamine treated DEPC-fibrin-D-dimer. Through this study it has been established that the PAV protease cleavage of the di-γ-chain of the plasmin derived D-dimer fragment is potentiated by zinc(II) ions through the formation of a novel zinc determined conformation of fibrin-D-dimer. This presents the possibility of a fibrinspecific neo-epitope being manifested in the presence of zinc ions that could provide a means to determine fibrin degradation products more specifically. A model for the neo-epitope has been proposed.
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Kumar, Rachana. "On the procoagulant effect of fibrin a resonance loop between fibrin - von Willebrand factor - platelets and thrombin /." [Maastricht : Maastricht : Universiteit Maastricht] ; University Library, Maastricht University [Host], 1997. http://arno.unimaas.nl/show.cgi?fid=5826.
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Bense, Christine Adelle. "The in vitro stability of cross-linked fibrin and fibrin/hyaluronan-coated polyurethanes in the presence of plasmin." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0012/MQ40903.pdf.
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De, Giorgio-Miller Alexander Michael. "The role of fibrin in skin fibrosis." Thesis, University College London (University of London), 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.397228.
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Davies, Thomas Marc. "Microstructure and mechanical properties of fibrin gels." Thesis, Swansea University, 2009. https://cronfa.swan.ac.uk/Record/cronfa42760.
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This thesis reports an extensive study of the structural and rheological characteristics of the three-dimensional fibrin clot network. The importance of blood clotting in the area of NanoHealth is testified to by the fact that complications due to thrombosis accounts for about 10 per cent of all deaths in hospitals in the UK. It is therefore imperative to understand the clotting process of blood as fully as possible. The techniques implemented include confocal laser scanning microscopy, and rheo logical methods such as Fourier transform mechanical spectroscopy. Both techniques provide a foundation for performing a fractal analysis as a quantitative basis for defining, where appropriate, morphological/micro structural differentiation in clotting. Fractal analysis provides the framework for structural complexity and allows us to develop relationships between the structural features of blood clots and their rheological properties. The experimental methods involve following the mechanical properties of a gelling system up to and beyond the gel point. The mechanical (viscoelastic) properties of fibrin are significant and unique among polymers. Hence, they are essential to the physiology of blood clotting and vital for the understanding and therefore prevention and treatment of thrombosis. An unsatisfactory aspect of work in this area is that the micro structures of such clots are usually reported in only adjectival terms (e.g., "dense" or "tight") - usually on the basis of a visual inspection of fragments of desiccated clots in SEM micrographs. This work includes an extensive approach using confocal microscopy to visualise fibrin clot networks, with several forms of fractal analysis investigated for quantifying structural complexity. The present study is the first to report a modification of the fractal characteristics of incipient clots in fibrin-thrombin gels due to the availability of thrombin. This work confirms the hypothesis that the self-similar (fractal) stress relaxation behaviour recorded at the Gel Point of samples of coagulating blood (Evans et al., 2008) is associated with the micro structural characteristics of the incipient blood clot's fibrin network. It also supports the hypothesis that in various pathologies prothrombotic conditions can modify the underlying micro structure of a blood clot. The provision of a new technique capable of detecting the formation of altered clot microstructures at their incipient state could have significant clinical diagnostic potential e.g. in thromboembolic disease screening applications.
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English, Elizabeth J. "Micropatterned Fibrin Hydrogels for Increased Cardiomyocyte Alignment." Digital WPI, 2019. https://digitalcommons.wpi.edu/etd-theses/1347.
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Cardiovascular disease is the leading cause of death in the US, which can result in blockage of a coronary artery, triggering a myocardial infarction (MI). After a MI, hypoxic ventricular myocardial tissue dies, resulting in the deposition of non-contractile scar tissue and remodeling of the ventricle, leading to decreased cardiac output and ultimately heart failure. Currently, the gold-standard solution for total heart failure is a heart transplant. As donor hearts are in short supply, an alternative to total-organ transplantation is surgically remodeling the ventricle with the implantation of a cardiac patch. Acellular cardiac patches have previously been investigated using synthetic or decellularized native materials in effort to improve cardiac function. However, a limitation of this strategy is that acellular cardiac patches only reshape the ventricle and do not increase cardiac contractile function. By incorporating the use of a clinically relevant cell type and by matching native architecture, we propose the use of a highly aligned fibrin scaffold to support the maturation of human induced pluripotent stem cell cardiomyocytes (hiPS-CM) for use as a cell-populated cardiac patch. By micropatterning fibrin hydrogels, hiPS-CM seeded on the surface of this scaffold become highly aligned, which is crucial for increased contractile output. Our lab previously developed a composite fibrin hydrogel and microthread cardiac patch matching mechanical properties of native myocardium. By micropatterning fibrin hydrogel alone, we were able to match cellular alignment of hiPS-CM to that of native myocardium. hiPS-CMs seeded on this surface were found to express distinct sarcomere alignment and circumferential connexin-43 staining at 14 days of culture as well as cellular elongation, which are necessary for mature contractile properties. Constructs were also cultured under electrical stimulation to promote increased contractile properties. After 7 days of stimulation, contractile strains of micropatterned constructs were significantly higher than unpatterned controls. These results suggest that the use of topographical cues on fibrin scaffolds may be a promising strategy for creating engineered myocardial tissue to repair damaged myocardium.
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Senderoff, Richard I. "Development of fibrin-based drug delivery systems /." The Ohio State University, 1990. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487677267728699.
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Bänninger, Hans Bänninger Hans. "Binding of alpha-thrombin to fibrin depends on the quality of the fibrin network : und ; Fibrin glue in surgery: frequent development of inhibitors of bovine thrombin and human factor V /." [S.l.] : [s.n.], 1996. http://www.ub.unibe.ch/content/bibliotheken_sammlungen/sondersammlungen/dissen_bestellformular/index_ger.html.
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Edgell, Tracey Ann. "An investigation of fibrin formation using specific monoclonal antibodies, and the development of an assay to detect soluble fibrin." Thesis, University of Hertfordshire, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.323431.
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Geer, Carri Brodnax Lord Susan T. "Analytical studies on the mechanism of fibrin formation." Chapel Hill, N.C. : University of North Carolina at Chapel Hill, 2007. http://dc.lib.unc.edu/u?/etd,1458.
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Thesis (Ph. D.)--University of North Carolina at Chapel Hill, 2007.Title from electronic title page (viewed Apr. 25, 2008). "... in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Chemistry with Emphasis in Biophysics." Discipline: Chemistry; Department/School: Chemistry.
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Abou-Saleh, Radwa Hassan. "Nanoscale structural and mechanical characterization of fibrin polymerisation." Thesis, University of Leeds, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.505059.
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Atomic Force Microscopy (AFM), along with other complementary biophysical techniques, has been used to study several important aspects of the blood clotting process. High resolution imaging modes were used to observe single monomers of fibrinogen, through to oligomers and initial stage proto-fibrils at sub-molecular resolution in order to understand the molecular basis of fibrin polymerization. Time resolved images of the developing clot were also taken at lower resolution appropriate to the scale of the features. The structures observed were correlated with turbidity measurements to plot the course of the reaction.
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Standeven, Kristina Felizitas. "Influences on fibrin formation, structure and cross-linking." Thesis, University of Leeds, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.413188.
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Grasman, Jonathan M. "Designing Fibrin Microthread Scaffolds for Skeletal Muscle Regeneration." Digital WPI, 2015. https://digitalcommons.wpi.edu/etd-dissertations/18.
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Volumetric muscle loss (VML) typically results from traumatic incidents; such as those presented from combat missions, where soft-tissue extremity injuries account for approximately 63% of diagnoses. These injuries lead to a devastating loss of function due to the complete destruction of large amounts of tissue and its native basement membrane, removing important biochemical cues such as hepatocyte growth factor (HGF), which initiates endogenous muscle regeneration by recruiting progenitor cells. Clinical strategies to treat these injuries consist of autologous tissue transfer techniques, requiring large amounts of healthy donor tissue and extensive surgical procedures that can result in donor site morbidity and limited functional recovery. As such, there is a clinical need for an off-the-shelf, bioactive scaffold that directs patient’s cells to align and differentiate into muscle tissue in situ. In this thesis, we developed fibrin microthreads, scaffolds composed of aligned fibrin material that direct cell alignment along the longitudinal axis of the microthread structure, with specific structural and biochemical properties to recreate structural cues lost in VML injuries. We hypothesized that fibrin microthreads with an increased resistance to proteolytic degradation and loaded with HGF would enhance the functional, mechanical regeneration of skeletal muscle tissue in a VML injury. We developed a crosslinking strategy to increase fibrin microthread resistance to enzymatic degradation, and increased their tensile strength and stiffness two- to three-fold. This crosslinking strategy enhanced the adsorption of HGF, facilitated its rapid release from microthreads for 2 to 3 days, and increased the chemotactic response of myoblasts twofold in 2D and 3D assays. Finally, we implanted HGF-loaded, crosslinked (EDCn-HGF) microthreads into a mouse model of VML to evaluate tissue regeneration and functional recovery. Fourteen days post-injury, we observed more muscle ingrowth along EDCn-HGF microthreads than untreated controls, suggesting that released HGF recruited additional progenitor cells to the injury site. Sixty days post-injury, EDCn-HGF microthreads guided mature, organized muscle to replace the microthreads in the wound site. Further, EDCn-HGF microthreads restored the contractile mechanical strength of the tissue to pre-injured values. In summary, we designed fibrin microthreads that recapitulate regenerative cues lost in VML injuries and enhance the functional regeneration of skeletal muscle.
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Wong, Cho Yi. "Characterization of Fibrin Matrix Incorporated Electrospun Polycaprolactone Scaffold." VCU Scholars Compass, 2016. http://scholarscompass.vcu.edu/etd/4103.
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Specific objective: Guided tissue regeneration (GTR) aims to regenerate the lost attachment apparatus caused by periodontal disease through the use of a barrier membrane. For the GTR procedures to be successful, barrier membranes are required to be present at the surgical site for an extended period of time (weeks to months). Synthetic membranes have the advantage of prolonged presence in a wound site; however, they do not actively contribute to wound healing. Biologic membranes are recognized by the host tissue and participate in wound healing but have the disadvantage of early resorption. Therefore, the goal of this study is to create and characterize a hybrid barrier membrane that contains biologically active fibrin matrix within a synthetic polymeric electrospun scaffold.
Method: Fibrin matrices and fibrin-incorporated electrospun scaffold were created from fresh frozen plasma at three different centrifugation conditions 400g for 12 minutes, 1450g for 15 minutes and 3000g for 60 minutes. Following centrifugation, half of the membranes were crosslinked with 1% genipin. Biological stability of these scaffolds was evaluated by resistance to trypsin while their mechanical properties were characterized by MTS Bionix Uniaxial Tensile Testing System. Continuous data was analyzed by ANOVA to detect differences between groups (p=0.05).
Results: The addition of an electrospun scaffold to the fibrin matrix led to improvements in the mechanical properties as evidenced by an increase in the modulus (p<0.0001), strain at break (p<0.0001) and energy to break (p<0.0001). The effect of crosslinking was marginal but not statistically significant to the mechanical properties of fibrin matrices or the fibrin incorporated scaffold. However, crosslinking did significantly increase resistance against enzymatic degradation by trypsin (p<0.0001). Lastly, centrifugation speeds at 400g and 1450g showed similar mechanical properties and biologic stability; meanwhile 3000g negatively impacted the properties of the scaffold.
Conclusion: Fibrin-incorporated electronspun scaffold exhibits enhanced mechanical and biologic stability compared to fibrin matrices alone. Moreover, crosslinking improves the biologic stability of the novel biomaterial. All these characteristics of the fibrin-incorporated matrix make this membrane a potentially more ideal barrier for GTR procedures to enhance periodontal wound healing.
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Badiei, Nafisheh. "Microstructural and rheological studies of fibrin-thrombin gels." Thesis, Swansea University, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.678597.
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Pan, Xiaoxi. "Fibrin clot structure alterations after particulate matter exposure." Thesis, University of Leeds, 2016. http://etheses.whiterose.ac.uk/14310/.
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Particulate matter (PM) as an important part of ambient air pollution has been associated with increased risks of cardiovascular diseases. Fibrin clot structure alteration is an emerging risk factor of many cardiovascular diseases, especially thrombosis. Therefore, the aim of this study was to investigate whether and how air particulate matter affects fibrin clot structure and endothelial cell behaviour. Turbidity assay, turbidity lysis assay and laser scanning confocal microscopy were used to analyse clots formed from normal pooled plasma or purified fibrinogen, in the presence of varying concentrations of PM. It was found that clots formed from plasma with higher concentrations of particles led to prolonged lysis time compared to control. No differences were seen for clots formed from fibrinogen. In a study of clots formed from plasma samples collected as part of a previous study on the effects of air pollution on deep vein thrombosis (DVT), alterations were observed in clots formed from plasma of DVT patients exposed to high levels of PM compared to those exposed to low levels, but the same differences were not observed in clots formed from plasma of control subjects. To investigate the potential role of venous endothelial cells in moderating clot structure following exposure to PM, human umbilical vein endothelial cells (HUVEC) were treated with PM for 24 hours and clots subsequently formed on the cells. Clots formed from plasma on the treated cells were altered compared to controls. RT-PCR and ELISA results showed increased gene expression of tissue factor (TF), protein expression of von Willebrand Factor (VWF) and plasminogen activation inhibitor-1 (PAI-1) and decreased thrombomodulin mRNA expression which were consistent with changes observed in clot structure. Engineered SiO2 nanoparticles caused denser clot structure in clots formed from normal pooled plasma. The gene expression of thrombomodulin was inhibited by SiO2 nanoparticles, but there were no significant difference in the TF mRNA expression between control and treated cells. Silica NPs caused increased concentrations of VWF, but not PAI-1 produced by endothelial cells. The results presented here show that PM can induce changes to clot structure and function, and that changes in gene expression induced in endothelial cells may be a mechanism by which a prothrombotic state is induced in response to PM exposure. Furthermore, some, but not all, similar changes were observed in clots and cells exposed to SiO2 nanoparticles, raising the possibility that such engineered nanoparticles may also have the potential to contribute to cardiovascular toxicity.
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Peck, M. Thabit. "The effect of storage time on the platelet concentration of Choukroun's platelet rich fibrin (PRF)." University of the Western Cape, 2011. http://hdl.handle.net/11394/5219.
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Magister Chirurgiae Dentium (MChD)Wound healing is a complex process characterised by the repair and reconstitution of lost or damaged tissue. By the mid 1990s, several methods were proposed to enhance wound healing of surgical sites by introducing high concentrations of human platelets to these areas. In the early 21st century, Choukroun et al (2006b) introduced a new type of platelet concentrate that was devoid of any additives, and required no specialised equipment for its production. This concentrate was termed Platelet-rich fibrin (PRF) and although various aspects of this biomaterial had been studied, very little is currently known about its storage properties. Aim: To determine whether storage time had a significant effect on the platelet concentration of Choukroun’s PRF Method: A total of 30 patients were enrolled into the study. Three blood samples of 10ml each were drawn from each patient. Two of the blood samples (Group A and Group B) were centrifuged to form PRF. The third sample was used to measure the baseline blood platelet concentration and was therefore not centrifuged. After PRF had formed in both test groups, it was removed from the test tubes at 2 different times i.e. immediately after centrifuge (Group A) or after 60 min of storage in the blood collecting tube (Group B). The remaining blood was then tested for platelet concentration and compared to each other and the baseline reading. Results: 14 males and 16 females participated in the study (average age 41.7 years). A mean blood platelet concentration of 282.8 ± 58.3 × 109/L was recorded for the baseline reading. Group A had a mean blood platelet concentration 7.9 ± 3.03 × 109/L. Group B had a mean blood platelet concentration of 4.0 ± 1.93 × 109/L. A statistically significant difference was seen between Groups A and B (p < 0.0001). Conclusions: Storage time has a significant effect of the platelet concentration of PRF. If stored over a period of 60 min, the platelet concentration of PRF increases. Further research is required to determine whether this finding is clinically significant.
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Lauster, Jörg. "Die Erlösungslehre Marsilio Ficinos : theologiegeschichtliche Aspekte des Renaissanceplatonismus /." Berlin : W. de Gruyter, 1998. http://catalogue.bnf.fr/ark:/12148/cb39900407p.
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Walker, John Berryhill. "The formation and cofactor activity of fibrin degradation products." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/NQ63466.pdf.
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Cornwell, Kevin G. "Collagen and fibrin biopolymer microthreads For bioengineered ligament regeneration." Link to electronic thesis, 2007. http://www.wpi.edu/Pubs/ETD/Available/etd-050407-104302/.
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Dissertation (Ph.D.) -- Worcester Polytechnic Institute.Keywords: Ligament; ACL; Collagen; Fibrin; Microthread; Fiber; Thread; FGF-2; Fibroblast; Tissue regeneration; Tissue engineering. Includes bibliographical references.
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Dunn, Emma Jane. "Determinants of fibrin structure and function : implications for fibrinolysis." Thesis, University of Leeds, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.424234.
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Pernis, Maria Grazia Roudaut François. "Le platonisme de Marsile Ficin et la Cour d'Urbin /." Paris : H. Champion, 1997. http://catalogue.bnf.fr/ark:/12148/cb36182436m.
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Th. Ph. D.--Hist. de l'art et de l'archéol.--New York--Columbia University, 1990. Titre de soutenance : Le platonisme de Ficin et la Cour d'Urbin : histoire des idées et histoire de l'art.Bibliogr. des oeuvres de Ficin p. 183-184. Bibliogr. p. 185-224.
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Santos, Johanna Eleanor. "Towards the Fabrication of a Fibrin Based Vascular Network." Digital WPI, 2018. https://digitalcommons.wpi.edu/etd-theses/1259.
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Physiologically relevant scaffold-based tissue engineered structures have been limited in scope and viability by the diffusion limits of oxygen and other nutrients and functions provided by native vasculature in vivo. This has prevented the maintenance of healthy cell populations in scaffolds that are more than 200痠 thick. Combining concepts from microfluidics with biomaterials engineering, this project set out to engineer a perfusable fibrin-based vascular network capable of physiologically relevant flow properties as well as diffusion that supports viable cell populations. To create this system, a small artery sized (1.5 mm wide) gelatin sacrificial structure was embedded inside of a block of robust fibrin gel (4.26% w/v fibrin) then melted and rinsed out to create a perfusable vascular network. Characterization consisted of morphometric and histological analyses for channel sizes compared to the sacrificial structures, particle tracking to observe flow properties, and fluorescent dextran diffusion to measure diffusivity into the fibrin scaffold. We found that channels derived from sacrificial structures maintain their size and shape inside of the gel. Flow properties of the fluid through the channels were found to be both laminar and within expected physiological rates compared to native vessels of similar sizes. Cells on the surface of the fibrin vascular device expressed fluorescent markers that were delivered through the vascular network and perfused through the fibrin scaffold. These findings suggest that a fibrin based vascular system may provide a platform creating a functional vascular layer and for developing tissue engineered systems of increased size and complexity.
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Marengo, Kaitlyn A. "The Incorporation of Decellularized Cardiac ECM into Fibrin Microthreads." Digital WPI, 2017. https://digitalcommons.wpi.edu/etd-theses/843.
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Stem cell therapies have shown promising capabilities in regaining the functionality of scar tissue following a myocardial infarction. Biological sutures composed of fibrin have been shown to more effectively deliver human mesenchymal stem cells (hMSCs) to the heart when compared to traditional cell delivery mechanisms. While the biological sutures do show promise, improvements can be made. To enhance the fibrin sutures, we propose to incorporate native cardiac extracellular matrix (ECM) into the fibrin microthreads to produce a more in vivo-like environment. This project investigated the effects that ECM incorporation has on fibrin microthread structure, mechanics, stem cell seeding, and pro-angiogenic potential. Single microthreads composed of fibrin or fibrin and ECM were subjected to uniaxial tensile testing. It was found that the microthreads consisting of both fibrin and ECM had significantly high elastic moduli than fibrin only microthreads. Cell seeding potential was evaluated by performing a 24-hour hMSC seeding experiment using sutures of the varying microthread types. A CyQuant cell proliferation assay was used to determine the number of cells seeded onto each suture type. The results determined that there was no statistical difference between the numbers of cells seeded on the types of sutures. To examine the pro-angiogenic potential the microthreads had, a 24-hour endothelial progenitor outgrowth cell (EPOC) outgrowth assay was used. Fibrin and 15% ECM-fibrin microthreads were placed within the scratch of an EPOC culture and evaluated every 6 hours for 24 hours. We found that the 15% ECM microthreads had significantly increased the EPOC outgrowth, approximately 16% more distance travelled than fibrin microthreads and 18% more than no microthreads. Our combined results suggest that ECM does not affect hMSC attachment to biological sutures but does increase the pro-angiogenic potential of the microthreads due to their increase in guiding EPOC outgrowth.
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Dohan, David. "Platelet Rich Fibrin (PRF) : modèle théorique et études préliminaires." Paris 5, 2005. http://www.theses.fr/2005PA05M004.
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Le PRF (Platelet Rich Fibrin) est un adjuvant chirurgical issu des technologies des colles de fibrine et des concentrés plaquettaires autologues de première génération (les PRP). L'objectif de ce travail est de réaliser une synthèse historique et technologique de cette famille d'adjuvants chirurgicaux à base de fibrine, de tenter de déterminer un premier modèle théorique de l'architecture moléculaire du PRF et enfin, à l'aide d'observations cliniques et d'analyses histologiques, d'évaluer le potentiel cicatriciel du PRF au niveau des tissus mous ainsi qu'au cours de la maturation des greffes osseusesPRF (Platelet Rich Fibrin) is a surgical additive coming from the autologous fibrin adhesives and first generation platelet concentrates (PRP) technologies. The objective of this work is to make a historical and technological synthesis of this family of fibrin related surgical additives, to create a first theoretical model of the PRF molecular architecture and finally, with clinical observations and histological analysis, to evaluate the healing potential of the PRF in soft tissue wounds and during bone graft maturation
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Hasan, Fadi K. "Characterization of Leukocyte-Platelet Rich Fibrin, a Novel Biomaterial." VCU Scholars Compass, 2015. http://scholarscompass.vcu.edu/etd/3749.
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Autologous platelet concentrates represent promising innovative tools in the field of regenerative medicine and are successfully used in oral surgery. Several commercial systems exist that generate various forms of platelet concentrates including Platelet-rich plasma (PRP) and Platelet-rich fibrin (PRF). The alpha- granules of entrapped platelets release a variety of peptide growth factors that promotes healing. Usually PRP is a suspension that can be injected into the site of injury or used as a gel with the addition of thrombin (PRP-gel). In contrast Choukroun’s L-PRF is a dense fibrin based biomaterial enriched with platelets and growth factors. The physical state of these natural biomaterials especially L-PRF permits manual handling and suturing onto the tissue bead to improve healing. However, our knowledge about the mechanical characteristic of L-PRF is quite limited and a good understanding of material properties will enable expansion of current clinical applications. This study demonstrates the techniques to identify L-PRF’s mechanical properties (uniaxial tensile testing and suture retention strength); morphology (scanning electron microscope); biological stability and cytocompatibility.
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Morin, Yvan. "L'âme et la raison chez Ficin et chez Descartes." Thesis, University of Ottawa (Canada), 1994. http://hdl.handle.net/10393/9803.
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Murphy, Megan K. "Fibrin microthreads promote stem cell growth for localized delivery in regenerative therapy." Worcester, Mass. : Worcester Polytechnic Institute, 2008. http://www.wpi.edu/Pubs/ETD/Available/etd-090208-143505/.
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Vu, Thi Bich Ngoc, Thi Thao Nguyen, Thi Hoa Chu, and Thi Tuyen Do. "Cloning and expression of recombinant thrombin in Escherichia coli JM109 (DE3)." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-227848.
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Prothrombin, a protein involved in blood coagulation, is a plasma glycoprotein composed of the Gla domain, two adjacent kringle domains, and a serine protease domain. Prothrombin is a thrombin precursor playing the important role in the coagulation physiological as well as pathological condition. Thrombin is the key to convert the fibrinogen into fibrin by switching activation of XIII factor, pushed plasminogen into plasmin, the develope of the fibroblast and helps the stabilization of thrombolysis. In this study, the prothrombin gene was 936 bp in lengths and encoded 312 amino acids from bovine lung was optimized codon, was cloned in pET21a+ vector and expression in E. coli, in order to replace traditional bandages having slow affect, reduce the cost of products, cater the comunity health. The results showed that initially the successful cloning and expression of recombinant prothrombin in E. coli JM109(DE3)Prothrombin, 1 glycoprotein huyết tương liên quan tới quá trình đông máu gồm 2 vùng Gla, 2 vùng Kringle và 1 vùng serine protease. Prothrombin là tiền chất của thrombin có vai trò quan trọng trong sinh lý đông máu cũng như tình trạng bệnh lý. Thrombin được xem như chìa khóa để chuyển hóa fibrinogen thành fibrin bằng cách hoạt hóa các yếu tố đông máu như XIII, thúc đẩy chuyển plasminogen thành plasmin và kích thích tăng sinh các tế bào tơ (fibroblast), giúp ổn định quá trình làm tan huyết khối. Trong nghiên cứu, các gen prothrombin được tách dòng từ phổi bỏ có kích thước 936 bp, mã hóa cho 312 axit amin được tối ưu hóa codon, nhân dòng vào vector pET21a+ và biểu hiện trong E. coli. Mục đích của nghiên cứu nhằm tạo ra băng gạc cầm máu nhanh, giá thành rẻ, phục vụ sức khỏe cộng đồng và thay thể băng gạc truyền thống. Kết quả nghiên cứu bước đầu cho thấy đã nhân dòng và biểu hiện thành công prothrombin tái tổ hợp ở chủng E. coli JM109(DE3)
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Jawerth, Louise Marie. "The Mechanics of Fibrin Networks and Their Alterations by Platelets." Thesis, Harvard University, 2013. http://dissertations.umi.com/gsas.harvard:10995.
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Fibrin is a biopolymer that assembles into a network during blood coagulation to become the structural scaffold of a blood clot. The precise mechanics of this network are crucial for a blood clot to properly stem the flow of blood at the site of vascular injury while still remaining pliable enough to avoid dislocation. A hallmark of fibrin's mechanical response is strain-stiffening: at small strains, its response is low and linear; while at high strains, its stiffness increases non-linearly with increasing strain. The physical origins of strain-stiffening have been studied for other biopolymer systems but have remained elusive for biopolymer networks composed of stiff filaments, such as fibrin. To understand the origins of this intriguing behavior, we directly observe and quantify the motion of all of the fibers in the fibrin networks as they undergo shear in 3D using confocal microscopy. We show that the strain-stiffening response of a clot is a result of the full network deformation rather than an intrinsic strain-stiffening response of the individual fibers. We observe a distinct transition from a linear, low-strain regime, where all fibers avoid any internal stretching, to a non-linear, high-strain regime, where an increasing number of fibers become stretched. This transition is characterized by a high degree of non-affine motion. Moreover, we are able to precisely calculate the non-linear stress-strain response of the network by using the strains on each fiber measured directly with confocal microscopy and by assuming the fibers behave like linearly elastic beams. This result confirms that it is the network deformation that causes the strain-stiffening behavior of fibrin clots. These data are consistent with predictions for low-connectivity networks with soft, bending, or floppy modes. Moreover, we show that the addition of small contractile cells, platelets, increases the low-strain stiffness of the network while the high-strain stiffness is independent of the presence of the platelets; this is also consistent with expectations for small contractile elements in a network with low connectivity. Our results elucidate the origins of strain-stiffening in fibrin networks as well as the mechanism underlying platelet-induced clot stiffening.Physics
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Dietl, Susanne Verfasser], and Clemens [Akademischer Betreuer] [Knospe. "Adipose tissue engineering in fibrin / Susanne Dietl. Betreuer: Clemens Knospe." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2016. http://d-nb.info/1106098250/34.
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Alston, Steven M. "Autologous Fibrinogen Purification and Concentration For Use in Fibrin Sealant." BYU ScholarsArchive, 2005. https://scholarsarchive.byu.edu/etd/443.
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Fibrinogen concentrates are used widely as a sealant during and after surgery to reduce blood loss. Commercially available fibrin sealants are made from pooled human blood, which carries the risk of blood-borne diseases, and are expensive. These concerns have brought to focus the need for autologous fibrinogen concentrates. This need has been addressed by utilizing a unique approach in which fibrinogen is precipitated from plasma with protamine. The physical properties of fibrin sealant prepared from fibrinogen precipitated with protamine were evaluated. The optimal precipitation conditions included a plasma protamine concentration of 10 mg/mL at room temperature. Under these conditions 96% ± 4% of the fibrinogen present in the plasma was precipitated and 98% ± 0.9% of the precipitated fibrinogen was clottable. In addition, it was shown that almost 50% of the factor XIII in the plasma was also precipitated along with the fibrinogen. The tensile and adhesion strengths and kinetics of fibrin sealant prepared from protamine-fibrinogen concentrate were evaluated. Tensile strength and adhesion strength both increased with increasing fibrinogen concentration. Addition of calcium chloride significantly increased the tensile and adhesion strengths. The addition of aprotinin and ε-aminocaproic acid (used to inhibit natural fibrinolysis) to the fibrinogen concentrate was shown to have no effect on the mechanical properties of the sealant. Kinetic experiments showed that the clotting time decreased as the thrombin and fibrinogen concentrations were increased. A rat model with controlled renal incisions was employed to evaluate the hemostatic efficacy of the fibrin sealant made from the protamine-fibrinogen concentrate. The fibrin sealant significantly reduced the blood loss and bleeding time when compared with controls (no sealant, plasma, and a commercial product). The sealant also significantly reduced blood loss and bleeding time in rats that were anticoagulated with heparin. A mathematical model based on tensile strength and adhesion strength was developed to predict the bleeding time in the animal wound. Model predictions showed that the ability of the fibrin sealant to reduce bleeding time, and therefore blood loss, was limited by the adhesion strength.
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Chrobak, Megan O'Brien. "Designing Modular Fibrin Composite Scaffolds for Enhanced Ventricular Myocardium Regeneration." Digital WPI, 2017. https://digitalcommons.wpi.edu/etd-dissertations/554.
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Cardiovascular diseases are the leading causes of death globally. One contributing factor that can lead to heart failure is a myocardial infarction. When an infarct occurs, an occlusion in the tissue vasculature prevents blood flow beyond this site. It results in scar tissue formation. The scar is non-contractile and reduces the working efficiency of the heart. To compensate, left ventricular remodeling will ensue resulting in enlarging of the left ventricle. This progression of events ultimately culminates in heart failure. One approach to assist patients who have suffered a heart attack is to implant a cardiac patch. Current patches are acellular and aim to retain the geometry of the left ventricle, limiting any ventricular remodeling from occurring. While these patches provide a passive support, it is hypothesized that incorporation of cells into the patches could result in functional support that could help to restore baseline function. To be effective, a cell-populated cardiac patch would need to integrate with the host tissue functionally and mechanically. In this thesis, we developed a fibrin microthread-based composite scaffold with material properties comparable to left ventricular myocardium that promotes regional cardiomyocyte alignment and physiologically relevant contractile strains. We hypothesized that a composite material could be developed where constituents of the material would complement one another to yield a mechanically reinforced scaffold that promotes cardiomyocyte function. Through manipulation of the volume fraction of the components, we manipulated the modulus of the layer without compromising contractile strain or contractile frequency of incorporated cells. Additionally, through strategic restraint of the scaffolds, we utilized cell-mediated compaction to induce a tension pattern that increased alignment of incorporated cells. This corresponded to an increase in contractile strain magnitudes, and an anisotropic contractile wave propagation through the engineered tissue. Finally, we laminated composite layers into a patch mimicking the architecture of ventricular myocardium and found that material properties of the patch were similar to properties of the target tissue. In summary, we designed a biomimetic composite patch with material properties similar to ventricular myocardium that supports cardiomyocyte alignment and contractility to promote functional and mechanical integration upon implantation.
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Routledge, Kathryn Emma. "New insights into b-2microglobulin fibrin formation using systematic mutagenesis." Thesis, University of Leeds, 2007. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.485785.
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De, Lange Albe Carina. "Ultrastructural analysis of platelets and fibrin networks in stroke patients." Diss., University of Pretoria, 2010. http://hdl.handle.net/2263/30763.
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Ischaemic stroke represent more than 80% of the total stroke instances. The location of the occlusion and the amount of brain tissue involved determines the effect of the stroke. Stroke can result in paralysis, memory loss, speech impairment and even a “lock-in” state. The amount of neuronal damage will determine whether these symptoms will be temporary or permanent. Stroke is deemed the second leading cause of death for individuals over the age of 60. According to the World Stroke Organization (WSO) every six seconds stroke claims a life, regardless of age or gender. Stroke is a global burden and the medical costs and disability related to stroke in America for 2010 was projected at almost $73.7 billion. The morphology of platelets, fibrin networks and erythrocytes as well as the differential white blood cell counts of 20 thrombo-embolic ischaemic stroke patients were investigated. Internal and external alterations were revealed in the platelets of stroke patients when compared to healthy controls. The decreased numbers of alpha granules in the platelets of the stroke patients indicated these platelets to be activated. Substances released by activated platelets promote fibrin network structure, specifically the formation of fibrin strands and accumulation of additional platelets. The fibrin network of healthy individuals consists of major, thick fibers with minor, thin fibers distributed between them. The fibrin network of stroke patients exhibited an abnormally layered and matted ultrastructure comprising of mainly thin, minor fibrin fibers packed closely together. An uncharacteristic circular morphology was also observed. These alterations in the fibrin network indicate the activated platelets to be actively involved in the thrombotic event. Neuronal damage related to stroke is also advanced by the vasoactive substances released by activated platelets. It can therefore be deduced that the morphology of the fibrin network is altered long before the concrete thrombotic event transpire. Large numbers of abnormal erythrocytes were distinguished in the blood of stroke patients. Among these abnormal forms of erythrocytes specifically codocytes, knizocytes, stomatocytes and echinocytes were identified. Abnormal erythrocyte forms were significantly increased in hypertensive patients and females independently. Alterations in the ultrastructure of erythrocytes disturb blood flow in the microcirculation and could possibly augment the ischaemic event. Inflammation is closely related to ischaemic stroke. An increased monocyte count and a reduced number of neutrophils were a significant feature among all the stroke patients of this study. Patients with hypertension as well as patients consuming aspirin on a daily basis showed the greatest influence on the observed differential white blood cell counts. These morphological alterations observed in the platelets, fibrin network and erythrocytes as well as the differential white blood cell count could be incorporated in an analysis regime that could probably indicate an impending thrombotic event. Therefore treatment could be initiated before the ischaemic event to possibly prevent the stroke. For future studies a larger study population, a more refined patient enrolment as well as the analysis of follow-up blood samples from patients could substantiate the above-mentioned findings and provide additional information concerning the thrombotic event and the effectiveness of treatment procedures.Dissertation (MSc)--University of Pretoria, 2010.
Anatomy
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Kirsch, Richard. "Characterisation of fibrinogen and fibrin proteolysis by the neutrophil membrane." Doctoral thesis, University of Cape Town, 1999. http://hdl.handle.net/11427/26928.
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Recent studies have identified a novel 600 kDa neutrophil membrane associated protease which degrades fibrinogen, fibrin and C-reactive protein (CRP) during incubation of these ligands with phorbol 12-myristate 13-acetate (PMA, 5-10 ng/ml) stimulated neutrophils. This proteolysis is predominantly an extracellular event which occurs through a ligand dependent release of this protease from the neutrophil. Degradation products arising from this proteolysis not only become neutrophil associated but influence a number of important processes occurring in inflammation and coagulation. The aim of the present 'study was to purify and further characterize this protease and investigate the location of the neutrophil associated fibrinogen and fibrin degradation products. Whilst enzyme purification procedures were unsuccessful, several observations made during these attempts suggested that the neutrophil membrane associated proteolytic activity displayed similar characteristics to proteases of the azurophil granule. The proteolytic activity of the membrane was concluded from inhibitor profiles, zymography, and the apparent molecular mass values and hydrophobicity of the fibrinogen degradation products that it generated, to be the composite action of the azurophil granule proteases, human neutrophil elastase, cathepsin G and possibly proteinase 3. Electron microscopy analysis of PMA stimulated neutrophils incorporated within fibrin clots revealed morphological changes suggestive of neutrophil degranulation, and the proteolytic activity released by these cells was shown to be identical to that of azurophil granule proteases with respect to the apparent molecular mass values of the fibrin products that it generated. Immunoelectron microscopy revealed minimal internalization of fibrin like material during this process suggesting that neutrophil mediated fibrinolysis under these conditions is predominantly an extracellular event. Immunoelectron microscopy was used to localise fibrinogen degradation products previously reported to be associated with the neutrophil following incubation with fibrinogen. This revealed neutrophil associated fibrinogen products to be intracellular. Internalisation appears to be the result of pinocytosis which is stimulated in the presence of PMA. Although internalisation may be enhanced by an initial interaction of fibrinogen with the neutrophil membrane, a large proportion of uptake occurs via the fluid phase. Both intact and degraded forms of fibrinogen can associate with the neutrophil. Internalised material is rapidly degraded intracellularly into low molecular weight products which are partially released into the surrounding medium. This intracellular degradation, however, contributes minimally to the overall degradation of fibrinogen by neutrophils; the major pathway is extracellular. The demonstration in this· study, that the previously identified fibrinogen- fibrin- and CRP-degrading activity of the neutrophil membrane is due to azurophil granule proteases co-incides with numerous recent reports suggesting that membrane bound forms of these proteases, due to their ability to evade naturally occurring protease inhibitors, are the biologically relevant forms of these proteases. The membrane expression of azurophil granule proteases has recently been shown to be under the control of a variety of inflammatory mediators. Thus, neutrophil mediated degradation of fibrinogen, fibrin and CRP in vivo may be tightly controlled by the regulated expression of azurophil granule proteases on the neutrophil membrane.
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Thacker, Robert I. "Modulation of Human Dendritic Cell Activity by Adsorbed Fibrin(ogen)." University of Cincinnati / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1218553202.
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Harrand, Robert. "The Viscoelastic Properties of Fibrin Clots Studied Using Magnetic Tweezers." Thesis, University of Leeds, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.485168.
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Magnetic tweezers have been designed, constructed, calibrated and 'applied, for the first time, to the study of the mechanical properties of fibrin clots. Three-dimensional control over magnetic particle position was achieved with forces of ''100pN in X,Y and ''IOpN in Z, generated with 4.5JLm ·particles. Software was custom written to control both the operation of the electromagnets and data analysis of the-captured images. The performance of the magnetic tweezers was initially evaluated using model viscous and viscoelastic materials such as polyacrylamide, and was used to demonstrate that the viscosity of complex fluids such as protein solutions could be measured. The calibrated magnetic tweezers were then applied to the study of the viscoelastic properties of fibrin clot formation using recombinant and purified fibrinogen in collaboration with colleagues in the Leeds General Infirmary. The behaviour of wild type fibrinogen was compared with three variants, each of which had particular physiological releyance. Initial results revealed a Hookean response of the fibrin clots at low forces, strain hardening at higher forces, and an increase to a maximum value of G' over time. Des-B,BI-42, which is created by the enzymatic action of rattlesnake venom, showed a marked reduction in mechanical strength compared with wild type fibrin, and this was related to thinner fibrin fibres by atomic force microscopy studies and turbidity measurements. The polymorphism. B,BArg448Lys, a relatively common variant with a frequency of 10-15% in Caucasians, possesses an argenine to lysine substitution in the ,B-chain region, 13 amino acids away from the carboxyl-terminal. A marked increase in clot stiffness was observed for the 448Lys variant compared to the 448Arg type, in agreement with known links between ,B-chain polymorphisms and coronary heart disease. Addition of the crosslinker factor XIII increased clot stiffness in both fibrin types, with increases in Lys448 clot stiffness continuing after several hours. Fibrinogen samples from patients with type 1 diabetes taken before and after treatment were studied to investigate possible links between the patient's blood sugar control and clotting functions. A k~y symptom of dia betes is an increased level of clot stiffness, increasing the risk of myocardial infarction. Results reveal~ a positive correlation between improvements in sugar control and reductions in clot stiffness.
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Ficin, Marsile Favret Gilles. "De vita libri tres /." [S.l. : s.n], 1989. http://catalogue.bnf.fr/ark:/12148/cb366585655.
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Fromstein, Joanna Dawn. "Development and characterization of fibrin and hyaluronan coated biodegradable polyurethane films." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/MQ58742.pdf.
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