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331.
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A microrespiration device is decribed which uses a Clark electrode to measure the oxygen consumption or production of small and microscopic aquatic organisms in an open flow system. The construction and working principles of the device, which can measure oxygen consumptions as low as 0.5 nl · h−1, are described. The design of the apparatus permits parallel measurements under identical conditions with a single electrode. The device can be matched to various sizes of animal and oxygen consumption rates by means of specimen chambers of different volumes (6 μl, 35 μl, 140 μl) and a variable water flow rate. The microflow respiration device has been used successfully to measure the respiration of zooplankton and meiobenthos organisms as well as protozoans and has also been used successfully on board a research vessel.  相似文献   
333.
Flooded forests in 79 sample areas were studied throughout the country. Using multivariate methods, six community types were established: (i)Tilia cordata-Mercurialis perennis, (ii)Ulmus laevis-Allium ursinum, (iii)Populus tremula-Convallaria majalis, (iv)Alnus incana-Cirsium oleraceum, (v)Alnus glutinosa-Filipendula ulmaria and, (vi)Alnus glutinosa-Carex acutiformis. The species composition of these types is partly overlapping but the abundance proportions of species are clearly different and all types have several significant (P < 0.05) indicator species. Communities of the first type grow mainly on temporarily overmoistened Dystri-Gleyic Arenosols on floodplain terraces but sometimes also in lower areas close to a riverbed on Eutric Gleysols or Gleyic Fluvisols. The second and third types embrace communities on levees where mainly Eutric Gleysols or Gleyic Fluvisols are represented. Communities of the fourth type are characteristic of low levees or flat areas with Mollic Fluvisols or Eutric Gleysols. The communities of the fifth and sixth types represent floodplain backswamp black alder forests on Eutric Gleysols, Molli-Histic and Histic Fluvisols. The convergence of communities, i.e., a situation where plant communities growing in various hydrological conditions and on different soils can have similar structure and belong to one community type is rather conspicuous for floodplain forests. In the conditions of Estonia, like in the Central European and Scandinavian countries, it is reasonable to consider as floodplain forest not only those growing on Fluvisolssensu stricto but all forests that are almost annually regularly covered with flood-water at least for a couple of weeks; the amount of alluvial sediments is not a decisive criterion in this case.  相似文献   
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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.  相似文献   
336.
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.  相似文献   
337.
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.  相似文献   
338.
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.  相似文献   
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