Cross-linking of dermal sheep collagen using a water-soluble carbodiimide

A cross-linking method for collagen-based biomaterials was developed using the water-soluble carbodiimide 1-ethyl-3-(3-dimethyl aminopropyl)carbodiimide hydrochloride (EDC). Cross-linking using EDC involves the activation of carboxylic acid groups to give O-acylisourea groups, which form cross-links after reaction with free amine groups. Treatment of dermal sheep collagen (DSC) with EDC (E-DSC) resulted in materials with an increased shrinkage temperature (Ts) and a decreased free amine group content, showing that cross-linking occurred. Addition of N-hydroxysuccinimide to the EDC-containing cross-linking solution (E/N-DSC) increased the rate of cross-linking. Cross-linking increased the Ts of non-cross-linked DSC samples from 56 to 73 °C for E-DSC and to 86 °C for E/N-DSC samples, respectively. For both cross-linking methods a linear relation between the decrease in free amine group content and the increase in Ts was observed. The tensile strength and the high strain modulus of E/N-DSC samples decreased upon cross-linking from 18 to 15MPa and from 26 to 16MPa, respectively. The elongation at break of E/N-DSC increased upon cross-linking from 142 to 180%

Protocol TOP-Study (tacrolimus organ perfusion): a prospective randomized multicenter trial to reduce ischemia reperfusion injury in transplantation of marginal liver grafts with an "ex vivo" tacrolimus perfusion

Background: Critical organ shortage results in the utilization of extended donor criteria (EDC) liver grafts. These marginal liver grafts are prone to increased ischemia reperfusion injury (IRI) which may contribute to deteriorated graft function and survival. Experimental data have shown that the calcineurin inhibitor tacrolimus exerts protective effects on hepatic IRI when applied intravenously or directly as a hepatic rinse. Therefore, the aim of the present study is to examine the effects of an ex vivo tacrolimus perfusion on IRI in transplantation of EDC liver grafts. Methods/Design: The TOP-Study (tacrolimus organ perfusion) is a randomized multicenter trial comparing the ex vivo tacrolimus perfusion of marginal liver grafts with placebo. We hypothesize that a tacrolimus rinse reduces IRI, potentially improving organ survival following transplantation of EDC livers. The study includes livers with two or more EDC, according to Eurotransplant International Foundation’s definition of EDC livers. Prior to implantation, livers randomized to the treatment group are rinsed with tacrolimus at a concentration of 20 ng/ml in 1000 ml Custodiol solution and in the placebo group with Custodiol alone. The primary endpoint is the maximum serum alanine transamninase (ALT) level within the first 48 hours after surgery; however, the study design also includes a 1-year observation period following transplantation. The TOP-Study is an investigator-initiated trial sponsored by the University of Munich Hospital. Seven other German transplant centers are participating (Berlin, Frankfurt, Heidelberg, Mainz, Münster, Regensburg, Tübingen) and aim to include a total of 86 patients. Discussion: Tacrolimus organ perfusion represents a promising strategy to reduce hepatic IRI following the transplantation of marginal liver grafts. This treatment may help to improve the function of EDC grafts and therefore safely expand the donor pool in light of critical organ shortage. Trial register: EudraCT number: 2010-021333-31, ClinicalTrials.gov identifier: NCT0156409

Education for Democratic Citizenship: a review of research, policy and practice 1995-2005

This paper provides a synthesis of the scholarly literature on education for democratic citizenship (EDC) in the school sector in England since 1995. Following the publication of the Crick Report (QCA, 1998), citizenship education was introduced to secondary schools in 2002 as a statutory subject. Primary schools are also required to show, through inspection, how they are preparing learners for citizenship. The implementation of citizenship as a national curriculum subject in England is taking place during a period of constitutional reform and was the most significant innovation of curriculum 2000. Recent parallel initiatives in EDC are taking place elsewhere in the UK, in Europe and internationally. In both established democracies and newlyestablished democratic states, such as those of Eastern and Central Europe and Latin America, there is a recognition that democracy is essentially fragile and that it depends on the active engagement of citizens, not just in voting, but in developing and participating in sustainable and cohesive communities. The paper examines the role of EDC in responding to these political challenges, setting national policy developments in both European and international contexts and exploring the growing international consensus on human rights as the underpinning principles of EDC. It identifies some key themes within the research, such as diversity and unity; global and cosmopolitan citizenship; children as citizens; democratic schooling; students’ understandings of citizenship and democracy; the complementary roles of schools and communities; European citizenship; and the practicalities of implementing EDC at school level. It identifies some gaps in the research literature and concludes by proposing an on-going agenda for research

Hydrogen detection study

The effectiveness was assessed of a hydrogen (H2) detection concept for regenerative environmental control life support systems (EC/LSS). The concept evaluated was that utilized for the electrochemical depolarized concentrator (EDC) design, constructed, and tested for the EC/LSS space station prototype program. The EDC contains combustible gas detectors (CGDs) which were evaluated with H2. The CGDs were evaluated for linearity, position sensitivity, reproducibility, ambient effects, repeatability, speed of response, recovery time, and interchangeability. The effectiveness of CGDs located within the EDC for sensing H2 leaks at various line replaceable units in the subsystem was determined. The effects of H2 leak rate, H2 concentration of leaking gas and air currents in the vicinity of the EDC were determined. Proposed improvements for the H2 detection concept were documented and alternative H2 detection approaches were identified and analyzed

Stability of cross-linked collagen

Teoretická část této bakalářské práce pojednává o obecných vlastnostech kolagenu, který je nejčastěji rozšířeným vláknitým proteinem v těle, o síťování kolagenu, které vede ke zlepšení mechanických i chemických vlastností, a o široce využívaných síťovacích činidlech, především 1-ethyl-3-(3-dimethylaminopropyl) karbodiimidu (EDC). Dále se zabývá několika metodami stanovení EDC ve vodném roztoku. Experimentální část je zaměřena na praktické stanovení množství EDC, které zůstalo ve vodě použité k promývání vzorků po síťování. Cílem bylo zjistit, jestli současně používaná metoda promývání je dostatečná pro jisté aplikace nebo je potřeba ji upravit. I přesto, že sloučenina EDC je prakticky netoxická, může způsobovat zbarvení kolagenních materiálů po sterilizaci ozařováním. Vzhledem k tomu, že nebylo zjištěno jaké množství EDC může ve vzorku zůstat nebo jestli je nezbytné vymýt veškeré EDC, je obtížné rozhodnout jestli je promývací metoda dostatečná nebo není. Navíc je potřeba brát do úvahy i ostatní vedlejší produkty síťování kolagenu. Nicméně cílem této práce bylo pouze zhodnotit účinnost vymývání EDC z kolagenních vzorků. Pro síťování byly použity tři různé koncentrace EDC a následně byly vzorky vymývány po různě dlouhou dobu. Takto bylo získáno 48 vodných vzorků, které byly následně třikrát spektrofotometricky stanoveny. Výsledně bylo zjištěno, že pro běžně používanou koncentraci síťovacího činidla (50 mmol.l 1 EDC) postačuje promývat vzorky po dobu 30 minut v roztoku hydrogenfosforečnanu sodného (Na2HPO3) a následně promývat ve vodě čtyřikrát po dobu 15 minut s výměnou vody při každém kroku. Po těchto krocích klesla koncentrace EDC v promývací vodě pod 1 mol . l-1, pro nižší koncentrace síťovacího roztoku byla dostatečná i kratší doba promývání. Výsledky této bakalářské práce jsou pouze předběžné, a proto by mělo následovat další zkoumání této problematiky.Theoretical part of this bachelor thesis is based on general information about collagen, most common fibrous protein in body, collagen cross-linking; leading to its better mechanical and chemical properties; and widely used crosslinking agents, mainly based on 1-ethyl-3-(3 dimethylaminopropyl) carbodiimide (EDC). Furthermore it deals with several methods of quantifying EDC in aqueous solutions. Experimental part is concerned with the determination of EDC remained in water used for washing samples in order to purify them after the cross-linking. The goal is to find out if used washing method is adequate enough for certain application or if it needs some adjusting. Even if EDC is practically non-toxic, it provides side effects on colour of the collagenous material after the sterilization by irradiation. Since it has not been found in the literature what specific amount of EDC can stay in a sample or if it is necessary to be completely washed out. According the state-of-the-art, it is difficult to assessed if the washing method is sufficient or not. Moreover, there are also other side products of cross-linking collagen in the final collageneous products that have to be taken into account. However, the aim of this bachelor thesis is to evaluate washing EDC from the collagenous sample only. As for cross-linking method, three concentrations of EDC followed by washing samples for different periods of time were used. Following this method, 48 samples were prepared and three times measured using UV-VIS colorimetric assay. As a result it was found out that for commonly used concentration of cross-linking agent (50 mmol.l-1 of EDC) it is sufficient to wash samples for 30 min in solution of disodium phospnonate (Na2HPO3) followed by washing with water 4 times for 15 min with changing the water at each step. After these steps, the concentration of EDC in washing water was reduced up to 1 mol.l-1. For lower concentrations of cross-linking EDC solution it is sufficient even shorter washing time. Considering the preliminary results of this bachelor thesis, further investigation dealing with this topic should follow.

Information Guide: Информация о Европейском союзе из Русскийх источников

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Information Guide: Trade Policy

A guide to the European Union’s Trade Policy, with hyperlinks to sources of information within European Sources Online and on external website