Anreicherung von Morphogenetischen Substanzen in Lichtpflanzen von Acetabularia Mediterranea Unter dem Einfluss von Puromycin

Zusammenfassung Unter dem Einfluß von Puromycin, das spezifisch aber reversibel die Proteinsynthese blockiert, erfolgt in belichteten kernhaltigen Pflanzenteilen von Acetabularia mediterranea eine Anreicherung morphogenetischer Substanzen. Wie Transplantationsversuche zwischen A. mediterranea und A. crenulata zeigen, betrifft diese Anreicherung sowohl die artspezifischen als auch die nichtartspezifischen morphogenetischen Substanzen. Die Anreicherung wird durch Actinomycin stark gehemmt.Es wird diskutiert, welche Schlußfolgerungen daraus für die Natur der artspezifischen morphogenetischen Substanzen gezogen werden können.

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Accumulation of morphogenetic substances in plants of Acetabularia mediterranea in light under the influence of puromycin

Summary Morphogenetic substances are accumulated in nucleated parts of the alga Acetabularia mediterranea in light, if they are treated with puromycin, which inhibits specifically but reversibel protein synthesis. Transplantation experiments between A. mediterranea and A. crenulata show, that there was an accumulation of both species specific morphogenetic substances and also of nonspecies specific ones. This accumulation is strongly inhibited if the parts are treated with actinomycin together with puromycin.The conclusions, which can be drawn from these results for the nature of the species specific substances, are discussed.

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Mit 4 Textabbildungen     

The influence of solvent viscosity on the threshold values of primary tastes

To study the effect of viscosity on the stimulus and recognitionthresholds of the four primary tastes, four thickeners whichare relatively free of any specific taste and odour (methylcellulose, guar seed flour, carob seed flour and tara seed flour)were selected from a greater number of such substances availableand the stimulus and recognition thresholds at the four viscositylevels, 1, 10, 100 and 1 000 cP determined for sucrose, sodiumchloride, caffeine and citric acid. It was found that with increasingviscosity also the stimulus and recognition thresholds increasedwhich means that higher concentrations of the taste substancesare necessary to produce the same taste intensity at higherviscosity. Significant differences were found particularly atthe highest viscosity level of 1 000 cP as compared to 1 cP.By relating the individual values to the corresponding valueat 1 cP it is possible to determine, bymeans of the so-calledamplification factors, the concentration increase that is necessarytoproduce the same taste intensity as at 1 cP. On the basisof regression straight lines, this amplification factor canbe determined for all substances and taste qualities. It becameobvious in this way that not only viscosity is important butalso the kind of thickener used.     

Capture of proteins from mammalian cells in pilot scale using different STREAMLINE adsorbents

This presentation compares three different expanded bed matrices. STREAMLINE rProtein A, STREAMLINE SP-XL and STREAMLINE Chelating were monitored in respect to their ability to clarify the broth, to concentrate and to purify the distinct target protein. The capture of a mouse IgG₁ and a recombinant prothrombin (PT) was carried out in pilot scale using a 100-l bioreactor and STREAMLINE 100 and 200 columns, respectively. The robustness of the process was also estimated monitoring the expansion behaviour and the cell and debris concentrations during the load and in the eluat. In all cases the capture of the target proteins was comparable to conventional chromatographic systems. The purification success was mainly dependent on the selectivity of the ligand used. The affinity process resulted in a highly purified product. The ion exchanger and chelating material mainly concentrated the product. In all three cases 100 l of cell broth were successfully processed in one run. The robustness of the ion exchanger process was poor, because of strong cell matrix interaction. However, for the chelating and especially for the affinity matrix a highly reproducible process was obtained.     

Biocompatibility evaluation of densified bacterial nanocellulose hydrogel as an implant material for auricular cartilage regeneration

Bacterial nanocellulose (BNC), synthesized by the bacterium Gluconacetobacter xylinus, is composed of highly hydrated fibrils (99 % water) with high mechanical strength. These exceptional material properties make BNC a novel biomaterial for many potential medical and tissue engineering applications. Recently, BNC with cellulose content of 15 % has been proposed as an implant material for auricular cartilage replacement, since it matches the mechanical requirements of human auricular cartilage. This study investigates the biocompatibility of BNC with increased cellulose content (17 %) to evaluate its response in vitro and in vivo. Cylindrical BNC structures (Ø48?×?20 mm) were produced, purified in a built-in house perfusion system, and compressed to increase the cellulose content in BNC hydrogels. The reduction of endotoxicity of the material was quantified by bacterial endotoxin analysis throughout the purification process. Afterward, the biocompatibility of the purified BNC hydrogels with cellulose content of 17 % was assessed in vitro and in vivo, according to standards set forth in ISO 10993. The endotoxin content in non-purified BNC (2,390 endotoxin units (EU)/ml) was reduced to 0.10 EU/ml after the purification process, level well below the endotoxin threshold set for medical devices. Furthermore, the biocompatibility tests demonstrated that densified BNC hydrogels are non-cytotoxic and cause a minimal foreign body response. In support with our previous findings, this study concludes that BNC with increased cellulose content of 17 % is a promising non-resorbable biomaterial for auricular cartilage tissue engineering, due to its similarity with auricular cartilage in terms of mechanical strength and host tissue response.     

Transsynaptic Coordination of Synaptic Growth,Function, and Stability by the L1-Type CAM Neuroglian

The precise control of synaptic connectivity is essential for the development and function of neuronal circuits. While there have been significant advances in our understanding how cell adhesion molecules mediate axon guidance and synapse formation, the mechanisms controlling synapse maintenance or plasticity in vivo remain largely uncharacterized. In an unbiased RNAi screen we identified the Drosophila L1-type CAM Neuroglian (Nrg) as a central coordinator of synapse growth, function, and stability. We demonstrate that the extracellular Ig-domains and the intracellular Ankyrin-interaction motif are essential for synapse development and stability. Nrg binds to Ankyrin2 in vivo and mutations reducing the binding affinities to Ankyrin2 cause an increase in Nrg mobility in motoneurons. We then demonstrate that the Nrg–Ank2 interaction controls the balance of synapse growth and stability at the neuromuscular junction. In contrast, at a central synapse, transsynaptic interactions of pre- and postsynaptic Nrg require a dynamic, temporal and spatial, regulation of the intracellular Ankyrin-binding motif to coordinate pre- and postsynaptic development. Our study at two complementary model synapses identifies the regulation of the interaction between the L1-type CAM and Ankyrin as an important novel module enabling local control of synaptic connectivity and function while maintaining general neuronal circuit architecture.