Transport of small anionic and neutral solutes through chitosan membranes: Dependence on cross-linking and chelation of divalent cations

Chitosan membranes were prepared by solvent casting and cross-linked with glutaraldehyde at several ratios under homogeneous conditions. The cross-linking degree, varying from 0 to 20%, is defined as the ratio between the total aldehyde groups and the amine groups of chitosan. Permeability experiments were conducted using a side-by-side diffusion cell to determine the flux of small molecules of similar size but with different chemical moieties, either ionized (benzoic acid, salicylic acid, and phthalic acid) or neutral (2-phenylethanol) at physiological pH. The permeability of the different model molecules revealed to be dependent on the affinity of those structurally similar molecules to chitosan. The permeability of the salicylate anion was significantly enhanced by the presence of metal cations commonly present in biological fluids, such as calcium and magnesium, but remained unchanged for the neutral 2-phenylethanol. This effect could be explained by the chelation of metal cations on the amine groups of chitosan, which increased the partition coefficient. The cross-linking degree was also correlated with the permeability and partition coefficient. The change in the permeation properties of chitosan to anionic solutes in the presence of these metallic cations is an important result and should be taken into consideration when trying to make in vitro predictions of the drug release from chitosan-based controlled release systems

Systemic proteasome inhibition triggers neurodegeneration in a transgenic mouse model expressing human α-synuclein under oligodendrocyte promoter: implications for multiple system atrophy

Multiple system atrophy (MSA) is a progressive late onset neurodegenerative α-synucleinopathy with unclear pathogenesis. Recent genetic and pathological studies support a central role of α-synuclein (αSYN) in MSA pathogenesis. Oligodendroglial cytoplasmic inclusions of fibrillar αSYN and dysfunction of the ubiquitin–proteasome system are suggestive of proteolytic stress in this disorder. To address the possible pathogenic role of oligodendroglial αSYN accumulation and proteolytic failure in MSA we applied systemic proteasome inhibition (PSI) in transgenic mice with oligodendroglial human αSYN expression and determined the presence of MSA-like neurodegeneration in this model as compared to wild-type mice. PSI induced open field motor disability in transgenic αSYN mice but not in wild-type mice. The motor phenotype corresponded to progressive and selective neuronal loss in the striatonigral and olivopontocerebellar systems of PSI-treated transgenic αSYN mice. In contrast no neurodegeneration was detected in PSI-treated wild-type controls. PSI treatment of transgenic αSYN mice was associated with significant ultrastructural alterations including accumulation of fibrillar human αSYN in the cytoplasm of oligodendroglia, which resulted in myelin disruption and demyelination characterized by increased g-ratio. The oligodendroglial and myelin pathology was accompanied by axonal degeneration evidenced by signs of mitochondrial stress and dysfunctional axonal transport in the affected neurites. In summary, we provide new evidence supporting a primary role of proteolytic failure and suggesting a neurodegenerative pathomechanism related to disturbed oligodendroglial/myelin trophic support in the pathogenesis of MSA

Oberflaechenbehandlung mit Laserstrahlen

Copy held by FIZ Karlsruhe; available from UB/TIB Hannover / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Untersuchungen zur Verbesserung der Schwingfestigkeit durch Randschichthaerten mit CO_2-Lasern

SIGLETIB: FR 4600 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Entwicklung und Bau von externen Laserkomponenten zum Haerten und Beschichten

Copy held by FIZ Karlsruhe; available from UB/TIB Hannover / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Randschichthaerten mit dem CO_2-Hochleistungslaser

Copy held by FIZ Karlsruhe; available from UB/TIB Hannover / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

OSIRIS. Erstarrung dispersionsverstaerkter einkristalliner Legierungen fuer Turbinenschaufeln mit Hilfe der Stuetzhauttechnologie Schlussbericht

In an interconnected project material scientific experiments were prepared for the German D2-Mission. Their runs were attended and the samples were investigated. The experiments contained remelting and controlled solidification of nickel base alloys from the cast and powder metallurgical condition. The PM-samples contained a five dispersion of sub-micron alumina particles. For shape preservation the turbine blade samples were provided with a ceramic skin. Four samples were processed under microgravity. The ceramic skin fulfilled its duty. The shape preservation was influenced by formation of gas bubbles in the PM-material. The microstructure showed a distinct agglomeration of the oxide particles. (orig.)In einem Verbundprojekt wurden werkstoffkundliche Experimente fuer die Deutsche D2 Mission 1993 vorbereitet, in der Durchfuehrung begleitet und ausgewertet. Die Experimente beinhalten das Umschmelzen und kontrollierte Wiedererstarren von Nickelbasislegierungen. Die Proben wiesen die Form von Turbinenschaufeln auf. Sie waren im Anlieferungszustand gegossen und pulvermetallurgisch hergestellt. Die heissisostatisch gepressten Proben enthielten eine feinverteilte Dispersion von Aluminiumoxidteilchen im sub-#mu#m-Bereich. Die Formerhaltung der Proben wurde mit einer keramischen Stuetzhaut vorgenommen. Vier Proben wurden in D2 Mission prozessiert. Die Stuetzhaut erfuellte ihre Funktion. Die Formerhaltung wurde durch die Entwicklung von groesseren Gasvolumina in den pulvermetallurgischen Proben beeintraechtigt. Die Gefuegeauswertung ergab eine deutliche Agglomeration zwischen den Oxidteilchen. (orig.)SIGLEAvailable from TIB Hannover: F96B35+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Forschung und Technologie (BMFT), Bonn (Germany); Deutsche Agentur fuer Raumfahrtangelegenheiten (DARA) GmbH, Bonn (Germany)DEGerman