Flow characterization of a wavy-walled bioreactor for cartilage tissue engineering

Cartilage tissue engineering requires the use of bioreactors in order to enhance nutrient transport and to provide sufficient mechanical stimuli to promote extracellular matrix (ECM) synthesis by chondrocytes. The amount and quality of ECM components is a large determinant of the biochemical and mechanical properties of engineered cartilage constructs. Mechanical forces created by the hydrodynamic environment within the bioreactors are known to influence ECM synthesis. The present study characterizes the hydrodynamic environment within a novel wavy-walled bioreactor (WWB) used for the development of tissue-engineered cartilage. The geometry of this bioreactor provides a unique hydrodynamic environment for mammalian cell and tissue culture, and investigation of hydrodynamic effects on tissue growth and function. The flow field within the WWB was characterized using two-dimensional particle-image velocimetry (PIV). The flow in the WWB differed significantly from that in the traditional spinner flask both qualitatively and quantitatively, and was influenced by the positioning of constructs within the bioreactor. Measurements of velocity fields were used to estimate the mean-shear stress, Reynolds stress, and turbulent kinetic energy components in the vicinity of the constructs within the WWB. The mean-shear stress experienced by the tissue-engineered constructs in the WWB calculated using PIV measurements was in the range of 0-0.6 dynes/cm2. Quantification of the shear stress experienced by cartilage constructs, in this case through PIV, is essential for the development of tissue-growth models relating hydrodynamic parameters to tissue properties.     

黄芪属一新改级

作者通过对药用黄芪野生资源的调查, 结合查阅大量标本及考证模式标本, 发现淡紫花黄芪Astrasalus membranaceus(Fisch. exLink)Bge. var. membranaceus f. purpurinus(Y. C. Ho)Y. C. Ho不仅花旗瓣顶端为紫红色;而且花小;小叶小, 质地厚, 小叶对数少;果小且果皮厚;限分布于我国西南地区。认为作为亚种处理比较合适。即A. membranaceus(Fisch. exLink)Bge. subsp. pallidipurpureus(Hsiao)X. Y. ZhuetC. J. Chen.     

Stretchable Lithium‐Ion Batteries Enabled by Device‐Scaled Wavy Structure and Elastic‐Sticky Separator

Fast developments and substantial achievements have been shaping the field of wearable electronic devices, resulting in the persistent requirement for stretchable lithium‐ion batteries (LIBs). Despite recent progress in stretchable electrodes, stretching full batteries, including electrodes, separator, and sealing material, remains a great challenge. Here, a simple design concept for stretchable LIBs via a wavy structure at the full battery device scale is reported. All components including the package are capable of being reversibly stretched by folding the entire pouch cell into a wavy shape with polydimethylsiloxane filled in each valley region. In addition, the stretchable, sticky, and porous polyurethane/poly(vinylidene fluoride) membrane is adopted as a separator for the first time, which can maintain intimate contact between electrodes and separator to continuously secure ion pathway under dynamic state. Commercial cathode, anode, and package can be utilized in this rationally designed wavy battery to enable stretchability. The results indicate good electrochemical performances and long‐term stability at repeatable release–stretch cycles. A high areal capacity of 3.6 mA h cm^?2 and energy density of up to 172 W h L^?1 can be achieved for the wavy battery. The promising results of the cost‐effective wavy battery with high stretchability shed light on the development of stretchable energy storages.     

A new bacterial dehydrogenase oxidizing the lignin model compound guaiacylglycerol beta-O-4-guaiacyl ether

A lignin model compound, named in short guaiagylglycerol beta-guaiacyl ether (GGE), contains the beta-0-4 ether linkage that is common in the chemical structure of lignin. A Pseudomonas sp. (GU5) had been isolated as an organism able to grow with GGE as the sole source of carbon and energy. When grown on vanillate, the bacteria contained a NAD+ -dependent dehydrogenase converting GGE to a 355 nm absorbing product. The enzyme, named GGE-dehydrogenase, was purified about 160-fold using gel permeation, ion exchange on DEAE-Sephadex, and dye-ligand affinity chromatography. The new protein was about 52 kDa in apparent size with but one polypeptide chain after denaturation and reduction. According to several criteria, the product of GGE oxidation (Km = 12 microM) was identified as the corresponding conjugated ketone at the alpha-carbon of the C3 side-chain. The secondary alcohol function in GGE was apparently the sole target of the enzyme action. However the conversion of GGE into ketone catalyzed by the enzyme was only partial, and did not exceed 50%, probably because only one of the alpha-enantiomers was susceptible to enzyme attack. In contrast the ketone, either made by organic synthesis or by enzymic oxidation of GGE, could be totally reduced back to GGE (Km = 13 microM at pH 8.4, 8 microM at neutral pH), with NADH as the reductant, as confirmed by UV absorption and NMR spectra. Other model compounds with no primary alcoholic function, ether linkage or phenolic group were also substrates for the enzyme, confirming the specificity of GGE-dehydrogenase for the alpha-carbon position. Conjugation of the alpha-ketone with an adjacent phenolic nucleus interfered strongly with equilibrium constants and redox potentials of the system according to pH, and the enzyme displayed widely different optima with pH over 9 when oxidizing GGE, below 7 when reducing the ketone. Equilibrium studies showed that the ketone/GGE potential was -0.37 volt at pH 8.7, -0.23 volt at pH 7 (30 degrees C). The significance of this new dehydrogenase and its properties are discussed, especially in the general concern of lignin biodegradation.     

On the mechanism of reductive activation in the mode of action of some anticancer drugs

Bioactivation of a number of DNA-specific antitumor drugs depends on oxidoreduction. Bleomycin, neocarzinostatin and anthracycline glycosides are the best known among such drugs in terms of reductive activation processes. Their reduction results in short-lived radical or electrophilic intermediates attacking DNA stereospecifically. The physico-chemical properties of these drugs and the nature of DNA damage are reviewed. Models for DNA-intercalation, electron-donor systems involved in drug metabolisation, and the role of oxygen in radical reactions, are discussed in the light of recent reports.     

青春双歧杆菌的波状层次生长特征观察

通过观察青春双歧杆菌在体外培养条件出现波状层次生长的情况,了解该过程中青春双歧杆菌形态的改变及其生物学意义。采用青春双歧杆菌低浓度接种于BS固体平板培养基中,延长培养时间至6 d,使其单个菌落长成较大的菌落后,置4℃冰箱中2~4周,在其培养结束时和放置冰箱后对菌落及菌体形态特征进行观察。在特定的培养时间及其后的低温处理后,青春双歧杆菌部分菌落出现了半透明环和不透明环交替的层次状结构,在半透明环区域和不透明环区域,菌体的形态以及对温度的敏感性存在差异,且在透明环区域,菌体发生了自溶现象。证明青春双歧杆菌在一定条件下形成了波状层次生长过程,且在该过程中,青春双歧杆菌的生长、生存方式以及增殖方式均发生了适应性变化。     

Transformation chimique d'analogues du propyzamide sur supports solides: Argiles et complexes argilo-humiques

Summary The catalytic effect of synthetic argilo-humic complexes on chemical transformation of propyzamide and analogs is shown. This chemical transformation is easier when the phenyl group is substituted by electro-donating substituents. An increase of complexe moisture increases the rate of degradation. These relations between degradation rates in argilo-humic complexes and soils are discussed.

     

Do flowers wave to attract pollinators? A case study with Silene maritima

To answer the question whether flowers wave to attract pollinators, we determine: (1) the heritability of floral mobility; (2) whether wavy flowers attract more insects; (3) does the duration of pollination affect seed set; and (4) the relationship between seed set and floral mobility. The pollination ecology of Silene maritima was investigated. Flowers on stalks of different waviness were used to investigate the effect of floral movement on pollinator visits. There is heritable variation in both direct and indirect estimates of floral mobility. The highest insect total visitation times were associated with medium length thin stalks that were visited more frequently and by more insect species. Although mean individual visit durations were less than those of less mobile flowers, this was compensated for by increased visits. Observations of controlled pollinations show that when the visit times are low, so is seed set and therefore low and high mobility flowers might suffer from reduced fitness. Combining these observations provides a mechanism that could be driving stabilizing selection for flower stalk traits, with a trade-off applying between waving to attract pollinators and not being too mobile as to prevent effective pollination. Further evidence for stabilizing selection is provided by the relationship observed in the field between seed set and floral mobility where the highest levels of fitness was associated with intermediate levels of floral waving.