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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
721

Sustainable Reaction and Separation Systems

Newton, Elizabeth Lynn 17 August 2005 (has links)
With increasing environmental awareness and natural resource limitations, researchers must begin to incorporate sustainability into their process and product designs. One target for green engineering is in reaction and separation design. This is typically done in a wasteful and often toxic manner with organic solvents and lack of recycle. The following thesis discusses alternatives to these costly separations by means of ionic liquids, benign extraction, separation with carbon dioxide, and near critical water. Ionic liquids are combined with carbon dioxide to induce melting point depressions of up to 124 degrees Celsius. Using this system as a reaction medium will offer control over the reaction phases while utilizing green solvents. Benign extractions are performed on both ferulic acid and on proteins from biomass by replacing alkaline solvents and costly protein separation techniques with simple liquid-liquid extraction. This means simpler systems and less waste than from previous methods. This thesis also discusses an opportunity for more efficient separation and recycle of a pharmaceutical catalyst, Mn-Salen. Using carbon dioxide with the organic aqueous tunable solvent system, the reaction can be run homogeneously and the product and catalyst separated heterogeneously, thus creating an extremely efficient process. Lastly, near critical water is used as an extraction and reaction medium by extracting ferulic acid from Brewers Spent Grain and then catalyzing its transformation to 4-vinylguaiacol. In this manner a simple, benign process is used to turn waste into valuable chemicals. Although somewhat different, each of the studied processes strives to eliminate waste and toxicity of many commonly used reaction and separation techniques, thus creating safe and sustainable processes.
722

Protein engineering to explore and improve affinity ligands

Linhult, Martin January 2003 (has links)
<p>In order to produce predictable and robust systems forprotein purification and detection, well characterized, small,folded domains descending from bacterial receptors have beenused. These bacterial receptors, staphylococcal protein A (SPA)and streptococcal protein G (SPG), possess high affinity to IgGand / or HSA. They are composed of repetitive units in whicheach one binds the ligand independently. The domains foldindependently and are very stable. Since the domains also havewellknown three-dimensional structures and do not containcysteine residues, they are very suitable as frameworks forfurther protein engineering.</p><p>Streptococcal protein G (SPG) is a multidomain proteinpresent on the cell surface of<i>Streptococcus</i>. X-ray crystallography has been used todetermine the binding site of the Ig-binding domain. In thisthesis the region responsible for the HSA affinity of ABD3 hasbeen determined by directed mutagenesis followed by functionaland structural analysis. The analysis shows that the HSAbindinginvolves residues mainly in the second α-helix.</p><p>Most protein-based affinity chromatography media are verysensitive towards alkaline treatment, which is the preferredmethod for regeneration and removal of contaminants from thepurification devices in industrial applications. Here, aprotein engineering strategy has been used to improve thetolerance to alkaline conditions of different domains fromprotein G, ABD3 and C2. Amino acids known to be susceptibletowards high pH were substituted for less alkali susceptibleresidues. The new, engineered variants of C2 and ABD shownhigher stability towards alkaline pH. Also, very important forthe potential use as affinity ligands, these mutated variantsretained the secondary structure and the affinity to HSA andIgG, respectively. Moreover, dimerization was performed toinvestigate whether a higher binding capacity could be obtainedby multivalency. For ABD, binding studies showed that divalentligands coupled using non-directed chemistry demonstrated anincreased molar binding capacity compared to monovalentligands. In contrast, equal molar binding capacities wereobserved for both types of ligands when using a directed ligandcoupling chemistry involving the introduction and recruitmentof a unique C-terminal cysteine residue.</p><p>The staphylococcal protein A-derived domain Z is also a wellknown and thoroughly characterized fusion partner widely usedin affinity chromatography systems. This domain is consideredto be relatively tolerant towards alkaline conditions.Nevertheless, it is desirable to further improve the stabilityin order to enable an SPA-based affinity medium to withstandeven longer exposure to the harsh conditions associated withcleaning in place (CIP) procedures. For this purpose adifferent protein engineering strategy was employed. Smallchanges in stability due to the mutations would be difficult toassess. Hence, in order to enable detection of improvementsregarding the alkaline resistance of the Z domain, a by-passmutagenesis strategy was utilized, where a mutated structurallydestabilized variant, Z(F30A) was used as a surrogateframework. All eight asparagines in the domain were exchangedone-by-one. The residues were all shown to have differentimpact on the alkaline tolerance of the domain. By exchangingasparagine 23 for a threonine we were able to remarkablyincrease the stability of the Z(F30A)-domain towards alkalineconditions. Also, when grafting the N23T mutation to the Zscaffold we were able to detect an increased tolerance towardsalkaline treatment compared to the native Z molecule. In allcases, the most sensitive asparagines were found to be locatedin the loops region.</p><p>In summary, the work presented in this thesis shows theusefulness of protein engineering strategies, both to explorethe importance of different amino acids regarding stability andfunctionality and to improve the characteristics of aprotein.</p><p><b>Keywords:</b>binding, affinity, human serum albumin (HSA),albumin-binding domain (ABD), affinity chromatography,deamidation, protein A, stabilization, Z-domain, capacity,protein G, cleaning-in-place (CIP), protein engineering, C2receptor.</p>
723

In-vitro-Untersuchungen zu antifibrotischen Wirkungen von β-Adrenozeptoragonisten und Glucocorticoiden in primären equinen Bronchialfibroblasten

Bonicelli, Jana 24 November 2015 (has links) (PDF)
Einleitung: Die Pathogenese chronisch entzündlicher Atemwegserkrankungen ist mit zunehmender Schädigung und fibrotischen Umbauvorgängen und daraus resultierenden Einschränkungen physiologischer Funktionen verbunden. Bei der Recurrent Airway Obstruction (RAO) des Pferdes sind solche strukturellen Veränderungen häufig assoziiert mit Verdickung der Atemwegswand, subepithelialer Fibrose und Obstruktion der Atemwege. Bei RAO besteht die Standardtherapie darin, die Bronchokonstriktion mit β2-Agonisten und die Entzündung mit Glucocorticoiden aufzuhalten. In den letzten Jahrzehnten konnte jedoch gezeigt werden, dass nicht alle Patienten mit der empfohlenen Therapie ausreichend behandelt werden können und neue Ansatzpunkte der Therapie gefunden werden müssen. Daher konzentrieren sich neuere Forschungsarbeiten auf strukturelle Alterationen in den Atemwegen, das sogenannte Airway-Remodelling. Zielsetzung: In der vorliegenden Arbeit sollen zunächst primäre equine Bronchialfibroblasten (EBF) isoliert, charakterisiert und kultiviert werden. Im nächsten Schritt sollen in diesen Zellen die β2-Rezeptorexpression und –eigenschaften charakterisiert werden. Anschließend soll die Eignung dieser Zellen als Zellmodell zur Untersuchung der zellulären Proliferation und Transformation sowie der Regulation der de-novo-Synthese von extrazellulärer Matrix und deren Beeinflussung durch β2-Agonisten und Glucocorticoide allein oder in Kombination sowie TGF-β überprüft werden. Material und Methoden: Mittels enzymatischer Verdauung mit 0,25 % Trypsin werden die EBF aus den Bronchien von 10 gesunden Schlachtpferden isoliert und in DMEM kultiviert. Diese Zellen werden morphologisch, immunzytochemisch und funktionell in deren Eigenschaften in An- oder Abwesenheit von fetalem bovinem Serum (FBS) oder Pferdeserum (HS) charakterisiert. Die Dichte und Subtypverteilung von β-Adrenozeptoren wird mittels Radioligandbindungsstudien mit [125I]-(-)-Iodocyanopindolol in Gegenwart von Rezeptorsubtyp-selektiven β-Antagonisten (β2: ICI 118,551 und β1: CGP 20712A) in EBF untersucht. Der Einfluss von β2-Agonisten auf die Proliferation und Differenzierung der EBF sowie die Kollagensynthese wird mittels [3H]-Thymidineinbauassay, Bestimmung von Gesamtprotein und α-Smooth Muscle Aktin (α-SMA) mit Lowrymethode und Western Blot-Analyse bzw. [3H]-Prolininkorporationsassay ermittelt. Die statistische Signifikanz wird über einen t-Test für verbundene Stichproben oder eine One-Way-ANOVA mit nachfolgendem Dunnett’s Test ermittelt und das Signifikanzniveau wird P ≤ 0,05 festgelegt. Ergebnisse: EBF können im DMEM-Medium nur in Gegenwart von Serum langfristig wachsen und kultiviert werden. In serum-freiem Medium und unter vorübergehendem Serumentzug können EBF nicht anhaften bzw. lösen sie sich ab. Die Effekte von FBS und HS auf EBF sind allerdings unterschiedlich. FBS fördert die Zellproliferation und -verdopplungsrate sowie die Zellpassage bis zur Passage 20 signifikant besser als HS (max. 9 Passagen). Unter FBS entwickeln EBF eine für Fibroblasten charakteristische spindelförmige Morphologie aber eine schwache α-SMA-Expression, während unter HS die Zellen eine atypische, polygonale Morphologie zeigen, jedoch mit signifikant hohem α-SMA und Proteingehalt. Radioligandenbindungsstudien zeigen, dass EBF lediglich den β2-Adrenozeptorsubtyp mit einer maximalen Rezeptorendichte (Bmax) von 5037 ± 494 Bindungsstellen/Zelle exprimieren. Die Behandlung der EBF mit β-Agonisten (Clenbuterol, Salbutamol, Isoproterenol) führt konzentrationsabhängig zur Abnahme dieser Anzahl der Rezeptoren mit unterschiedlicher Wirkungsstärke (Clenbuterol > Salbutamol > Isoproterenol), wobei Dexamethason diese nicht verändert. Diese Agonisten sowie auch Dexamethason hemmen die Proliferation der EBF, und dies kann in Gegenwart von ICI 118,551 aber nicht von CGP 20712A gehemmt werden, was auf den Einfluss des β2-Adrenozeptors hinweist. β2-Agonisten und Dexamethason gemeinsam resultieren in einer verstärkten Hemmung der EBF-Proliferation. Transforming Growth Factor-β1 (TGF-β1) stimuliert die Transformation von EBF zu Myofibroblasten mit einer erhöhten Expression von α-SMA in EBF, welches eher durch Dexamethason als durch Clenbuterol gehemmt wird. Die Kollagensynthese wird nur durch Dexamethason signifikant gehemmt. Schlussfolgerung: Das erstmalig etablierte EBF-Kulturmodell dient der Erforschung von Signalwegen und neuen Arzneimitteltargets im Zusammenhang mit der Pathogenese der equinen RAO insbesondere dem Atemwegs-Remodelling. So kann gezeigt werden, dass die Verwendung von β2-Agonisten allein oder in Kombination mit Glucocorticoiden eine Hemmung der Proliferation und Transformation von EBF in vitro bewirkt. Dies deutet auf einen zusätzlichen therapeutischen Nutzen von Clenbuterol und Glucocorticoiden hin und impliziert die Notwendigkeit eines frühzeitigen Einsatzes dieser Pharmaka bei der RAO des Pferdes.
724

Überprüfung eines Serumproteinprofils für die Diagnostik von Glioblastomen / Review of a serum protein profile in the diagnosis of glioblastoma

Nawka, Peter 20 November 2013 (has links)
Die Diagnostik eines Glioblastoms (GBM) stützt sich z.Z. neben klinischer Symptomatik auf bildgebende Diagnostik sowie die histologische Untersuchung. In letzter Zeit werden zuneh-mend Serumproteine beschrieben und untersucht, die mit einer GBM-Erkrankung assoziiert sind. Elstner, Stockhammer und Kollegen haben 2011 ein Serumproteinprofil identifiziert, das aus CXCL10/IP-10, BMP-2 und HSP70 besteht und in einem Kollektiv von 23 GBM-Erkrankten und 9 Gesunden eine Sensitivität von 89% und eine Spezifität von 96% besaß. Dieses Profil wurde nun in einer unizentrischen klinischen Studie an 35 GBM-Erkrankten und 37 Patienten mit differenzialdiagnostisch relevanten Erkrankungen (v. a. Hirnmetastasen und primären ZNS-Lymphomen) überprüft. Dabei wurden die präoperativ abgenommenen Blut-proben mittels des ELISA-Nachweisverfahrens untersucht und die jeweiligen Konzentratio-nen in die von Elstner et al. (2011) entwickelte Regel eingesetzt. In diesem Kollektiv konnte das Profil nicht zwischen einem GBM und seinen Differenzialdiagnosen unterscheiden (Sensitivität 31%, Spezifität 54%). Es ist nicht als Hilfsmittel zur Diagnostik von Glioblastomen geeignet.
725

Lietuvos vietinių veislių arklių genetinė analizė / Genetic analysis of Lithuanian native horse breeds

Juras, Rytis 30 March 2005 (has links)
1. For the first time a wide range of biochemical genetic markers and different typing techniques were used to access levels of genetic variability in Lithuanian horse breeds; 2. DNA based methods were used to access levels of genetic variation in Lithuanian horse breeds; 3. Genetic variation in Lithuanian horses was investigated using mitochondrial DNA (mtDNA) sequencing; 4. Genetic relationship and genetic distances between the breeds were estimated using a wide range of different genetic markers.
726

A comparison between the effects of black tea and rooibos on the iron status of primary school children / Petronella Breet

Breet, Petronella January 2003 (has links)
Background: Clinical studies have shown that tea consumption leads to decreased iron absorption. This finding is however, not supported by epidemiological studies, where no relationship between an increased tea consumption and a lower iron status in a population at risk of iron depletion has been found. Objectives: The main aim of this study was to compare the effects of black tea and Rooibos consumption on the iron status of primary school children in a rural setting in Potchefstroom, South Africa. Methods: One hundred and seventy five children, aged six to fifteen years, participated in this single blind, randomised, parallel intervention trial. Subjects were randomly allocated to receive two 200ml servings of either black tea or Rooibos with milk and sugar. These beverages were consumed during breaks and at the same time as the food h m the school-feeding scheme. The trial proceeded for sixteen weeks. The children received antihelminthic treatment (500mg mebendazole) at baseline. Haemoglobii haematocrit, serum iron, ferritin and transferfin were measured and total iron binding capacity and transferrin saturation were calculated. Trained fieldworkers measured dietary intakes by means of 24-hour dietary recalls and anthropometrists took anthropometric measurements. All the above mentioned data were gathered at the beginning and at the end of the intervention period. Results: Measurements indicated a study population that is malnourished in terms of anthropometrical indices and nutrient intakes. Biochemical markers of iron status also indicated that the population could be at risk of iron depletion. Changes in red blood cell count, haemoglobin, haematocrit, mean corpuscular haemoglobin (MCH), mean corpuscular volume (MCV), serum iron, transferrin, transferrin saturation, ferritin and total iron binding capacity (TIBC) did not differ significantly between the two groups. Mean red blood cell count, haematocrit, MCV, transferrin and TIBC increased significantly h m baseline to end in both groups (all p<0.0001) and MCH decreased significantly (p<.0001). Mean haemoglobin increased significantly with black tea consumption (p=0.002), although not with the consumption of Rooibos (p=0.073). Conclusion: Black tea or Rooibos consumption has similar effects on the iron status of primary school children. Iron status was not compromised by black tea in comparison with Rooibos. This questions the proposed limitation of black tea consumption as a public health strategy in order to combat iron deficiency in a population with marginal iron status. / Thesis (M.Sc. (Nutrition))--North-West University, Potchefstroom Campus, 2004.
727

Prieširdžių virpėjimo po miokardo revaskuliarizacijos operacijų sąsaja su elektrolitų koncentracija serume bei ekskrecija su šlapimu / Relation of postoperative atrial fibrillation to serum electrolyte concentration and urinary electrolyte excretion after myocardial revascularization

Švagždienė, Milda 19 December 2006 (has links)
Postoperative atrial fibrillation (AF) after cardiac surgery with cardiopulmonary bypass (CPB) remains unresolved problem. Some authors noticed that there were changes in electrolyte balance after coronary artery bypass grafting (CABG) surgery with CPB. The changes in serum magnesium level and their relation with the rate of postoperative AF are usually analyzed in scientific publications. The aim of the study has been to estimate the relationship between the rate of postoperative AF and the changes in serum electrolyte concentration and their urinary excretion after CABG surgery with CPB. The goals: 1) To estimate the rate and the character of postoperative AF and its influence on haemodynamics after CABG surgery. 2) To estimate changes in serum K+, Na+, Mg++, Ca++, Cl–, P– concentration and compare them between the patients who received, and who did not receive magnesium sulphate supplementation during the surgery. 3)To estimate changes of urinary excretion of K+, Na+, Mg++, Ca++, Cl–, P– and compare them between the patients who received, and who did not receive magnesium sulphate supplementation during the surgery. 3) To evaluate the effects of intraoperatively infused magnesium sulphate on the rate of postoperative AF in the early postoperative period. In our study the rate of postoperative AF was 27.4 %. AF in 91.3 % of cases was tachyarrhythmic, but haemodynamic remained stabile. Serum Mg++ level was > 1.05 mmol/l during the suregry in all patients. The infusion of... [to full text]
728

Analysis of in vitro functions of mesenchymal stem cells isolated from different human tissues / Skirtingų suaugusio žmogaus audinių mezenchiminių kamieninių ląstelių funkcionavimo mechanizmų tyrimai

Tunaitis, Virginijus 07 March 2011 (has links)
Human mesenchymal stem cells (MSC) have attracted a great deal of interest for their potential use in regenerative medicine and suppression of the inflammation. Nevertheless, all known therapy protocols require large amounts of MSCs, which can be obtained only by in vitro expansion. One of the most important methodological problems is associated with the use of animal-derived components in the cell culture medium. The main aim of the current research was to elucidate the influence of different serum substitutes on the proliferation, differentiation, expression of cell surface markers, and total protein expression of mesenchymal stem cells derived from human adipose tissue. In addition we were aiming to determine the features of mesenchymal stem cell populations from an exfoliated deciduous tooth (SHED) and their response to the multifunctional proinflammatory protein alpha1-antitrypsin. Our results indicate that adipose tissue derived MSCs cultivated in the presence of fetal calf serum and allogeneic human serum display similar properties, while synthetic serum substitute induces increase in growth and differentiation potential of MSCs. Moreover, our results indicate, that synthetic serum substitute also activates transcription of genes related to adipogenic and osteogenic differentiation and diminishes expression of cell surface marker CD146. In the present study, we used a proteomic approach that allowed us to compare protein expression signatures between primary cell... [to full text] / Žmogaus suaugusio organizmo mezenchiminės kamieninės ląstelės (MKL) pradėtos sėkmingai naudoti pažeistų audinių regeneracijai ir uždegiminio proceso slopinimui. Šiuolaikiniams terapijos protokolams yra reikalingi dideli ląstelių kiekiai, todėl prieš naudojimą yra būtina jas padauginti in vitro. Tačiau naudojant skirtingus MKL išskyrimo, in vitro kultivavimo ir padauginimo protokolus, yra sunku lyginti mokslinių tyrimų duomenis ir klinikinių tyrimų rezultatus. Nevienodos kultivavimo sąlygos gali įtakoti MKL funkcines savybes (augimo greitį, gebėjimą diferencijuotis, migracinį aktyvumą ir kt.). Šiame disertaciniame darbe tyrėme auginimo terpių, praturtintų skirtingais serumais (gyvulinės kilmės serumai, žmogaus alogeninis serumas, sintetinis serumas), poveikį žmogaus riebalinio audinio MKL. Taip pat charakterizavome MKL išskirtas iš žmogaus pieninių dantų pulpos ir palyginome šių ląstelių kultūros bei jų dukterinių klonų savybės. Kompleksiškai tyrėme uždegimo antiproteinazės alfa1-antitripsino (AAT) poveikį šioms ląstelėms. Nustatėme, kad, lyginant su kitais tyrime naudotais serumais, sintetinis serumo pakaitalas geriausiai skatino MKL augimą bei gebėjimą diferencijuotis adipogenine ir osteogenine kryptimis. Taip pat, skirtingai nuo kitų naudotų gyvulinės kilmės ir žmogaus serumų, sintetinis serumo pakaitalas veikė kaip adipogeninės ir osteogeninės diferenciacijos indukcijai svarbių genų PPARγ ir Msx2 transkripcijos aktyvatorius. Be to, sintetinis serumo pakaitalas slopino... [toliau žr. visą tekstą]
729

Mechanisms that Jeopardize Skeletal Muscle Perfusion during Surgery

Mak, Timothy 05 December 2013 (has links)
We assessed potential mechanisms that may jeopardize skeletal muscle perfusion during surgery leading to adverse outcomes including muscle injury and flap hypoxia. In craniotomy patients, we observed an increase in serum lactate and creatine kinase and urine myoglobin; indicative of muscle damage. The early rise in lactate correlated with elevated BMI, suggesting that obesity caused tissue compression and muscle ischemia. In our rodent model, we investigated the effects of flap preparation and phenylephrine on muscle perfusion by assessing microvascular blood flow and tissue PO2. Phenylephrine reduced muscle blood flow by ~20%, yet increased PO2 by ~10% suggestive of decreased O2 metabolism. At baseline, muscle flap blood flow was reduced by ~50% while PO2 was severely reduced ~80% (~5 torr) suggesting that flap perfusion was attenuated and O2 metabolism was increased. Phenylephrine infusion further reduced muscle flap perfusion. These data demonstrate multiple mechanisms by which muscle perfusion is jeopardized during surgery.
730

Mechanisms that Jeopardize Skeletal Muscle Perfusion during Surgery

Mak, Timothy 05 December 2013 (has links)
We assessed potential mechanisms that may jeopardize skeletal muscle perfusion during surgery leading to adverse outcomes including muscle injury and flap hypoxia. In craniotomy patients, we observed an increase in serum lactate and creatine kinase and urine myoglobin; indicative of muscle damage. The early rise in lactate correlated with elevated BMI, suggesting that obesity caused tissue compression and muscle ischemia. In our rodent model, we investigated the effects of flap preparation and phenylephrine on muscle perfusion by assessing microvascular blood flow and tissue PO2. Phenylephrine reduced muscle blood flow by ~20%, yet increased PO2 by ~10% suggestive of decreased O2 metabolism. At baseline, muscle flap blood flow was reduced by ~50% while PO2 was severely reduced ~80% (~5 torr) suggesting that flap perfusion was attenuated and O2 metabolism was increased. Phenylephrine infusion further reduced muscle flap perfusion. These data demonstrate multiple mechanisms by which muscle perfusion is jeopardized during surgery.

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