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991.
Melanie Bok Haiyan Li Leslie Y. Yeo James R. Friend 《Biotechnology and bioengineering》2009,103(2):387-401
Flow visualization using fluorescent microparticles and cell viability investigations are carried out to examine the mechanisms by which cells are seeded into scaffolds driven by surface acoustic waves. The former consists of observing both the external flow prior to the entry of the suspension into the scaffold and the internal flow within the scaffold pores. The latter involves micro‐CT (computed tomography) scans of the particle distributions within the seeded scaffolds and visual and quantitative methods to examine the morphology and proliferation ability of the irradiated cells. The results of these investigations elucidate the mechanisms by which particles are seeded, and hence provide valuable information that form the basis for optimizing this recently discovered method for rapid, efficient, and uniform scaffold cell seeding. Yeast cells are observed to maintain their size and morphology as well as their proliferation ability over 14 days after they are irradiated. The mammalian primary osteoblast cells tested also show little difference in their viability when exposed to the surface acoustic wave irradiation compared to a control set. Together, these provide initial feasibility results that demonstrate the surface acoustic wave technology as a viable seeding method without risk of denaturing the cells. Biotechnol. Bioeng. 2009;103: 387–401. © 2009 Wiley Periodicals, Inc. 相似文献
992.
Nutrient transport limitation remains a fundamental issue for in vitro culture of engineered tissues. In this study, perfusion bioreactor configurations were investigated to provide uniform delivery of oxygen to media equivalents (MEs) being developed as the basis for tissue‐engineered arteries. Bioreactor configurations were developed to evaluate oxygen delivery associated with complete transmural flow (through the wall of the ME), complete axial flow (through the lumen), and a combination of these flows. In addition, transport models of the different flow configurations were analyzed to determine the most uniform oxygen profile throughout the tissue, incorporating direct measurements of tissue hydraulic conductivity, cellular O2 consumption kinetics, and cell density along with ME physical dimensions. Model results indicate that dissolved oxygen (DO) uniformity is improved when a combination of transmural and axial flow is implemented; however, detrimental effects could occur due to lumenal pressure exceeding the burst pressure or damaging interstitial shear stress imparted by excessive transmural flow rates or decreasing hydraulic conductivity due to ME compaction. The model was verified by comparing predicted with measured outlet DO concentrations. Based on these results, the combination of a controlled transmural flow coupled with axial flow presents an attractive means to increase the transport of nutrients to cells within the cultured tissue to improve growth (increased cell and extracellular matrix concentrations) as well as uniformity. Biotechnol. Bioeng. 2009; 104: 1197–1206. © 2009 Wiley Periodicals, Inc. 相似文献
993.
Stefan Stich Marion Haag Thomas Häupl Orhan Sezer Michael Notter Christian Kaps Michael Sittinger Jochen Ringe 《Cell and tissue research》2009,336(2):225-236
In situ tissue engineering is a promising approach in regenerative medicine, with the possibility that adult stem or progenitor
cells will be guided chemotactically to a tissue defect and subsequently differentiate into the surrounding tissue type. Mesenchymal
stem cells (MSC) represent attractive candidate cells. Chemokines such as CXCL12 (SDF-1α) chemoattract MSC, but little is
known about the molecular processes involved in the chemotaxis and migration of MSC. In this study, MSC recruitment by CXCL12
was investigated by genome-wide microarray analysis. The dose-dependent migration potential of bone-marrow-derived MSC toward
CXCL12 was measured in an in vitro assay, with a maximum being recorded at a concentration of 1,000 nM CXCL12. Microarray
analysis of MSC stimulated with CXCL12 and non-stimulated controls showed 30 differentially expressed genes (24 induced and
six repressed). Pathway analysis revealed 11 differentially expressed genes involved in cellular movement and cytokine-cytokine
receptor interaction, including those for migratory inducers such as the chemokines CXCL8 and CCL26, the leukocyte inhibitory
factor, secretogranin II, and prostaglandin endoperoxide synthase 2. These results were confirmed by real-time polymerase
chain reaction for selected genes. The obtained data provide further insights into the molecular mechanisms involved in chemotactic
processes in cell migration and designate CXCL12 as a promising candidate for in situ recruitment in regenerative therapies.
Stefan Stich and Marion Haag contributed equally to this work.
This study was supported by the Investitionsbank Berlin and the European Regional Development Fund (grant: 10128098), Deutsche
Forschungsgemeinschaft (grant: DFG SI 569/7–1), and the Bundesministerium für Bildung und Forschung (Bioinside: 13N9817). 相似文献
994.
Syed G. Dastager Ashok Pandey Jae-Chan Lee Wen-Jun Li Chang-Jin Kim 《Current microbiology》2009,59(1):21-29
Aerobic, alkaliphilic to alkalitolerant and mesophilic bacteria were isolated and characterized from soil and sediment samples
collected from Bigeum Island, South Korea. The total numbers of microorganisms in the soil and sediment samples were found
to be 103–105 cfu/g and 102–107 cfu/g, respectively. A total of 163 isolates were isolated and subjected to further characterization on the basis of pH,
temperature and salt tolerance. Among the 163 isolates, 54 were selected based on their tolerance attributes to temperature,
pH and NaCl. Out of the 54 isolates, 27 were further selected based on their multiple tolerance ability and enzyme profile
and were subjected to 16S rRNA gene sequencing and phylogenetic analysis. The latter indicated that most of the Bigeum Island
isolates were related to the phylum Actinobacteria. The phylogenetic tree based on 16S rRNA gene sequences placed the 27 isolates into 9 different major bacterial genera, each
genus comprising pure cultures that shared ≤97% sequence identity and 18 putative novel species. Most of the strains were
alkalitolerant and mesophilic, and produced biotechnologically important enzymes at alkaline pH. 相似文献
995.
Z. Petek akar Ceren Alkm Burcu Turanl Nilgün Tokman Süleyman Akman Mehmet Sarkaya Candan Tamerler Laurent Benbadis Jean M. Franois 《Journal of biotechnology》2009,143(2):130-138
Cobalt is an important element with magnetic properties used in various industrial applications, but is also needed for biological activity. Very little is known about the cellular response of living systems to cobalt stress. Towards investigating this mechanism, we isolated individual Saccharomyces cerevisiae cells resistant to high cobalt concentrations up to 8 mmol l−1, by employing four different ‘in vivo’ evolutionary engineering strategies: selection under constant or gradually increasing stress levels, and selection under continuous or pulse exposure to cobalt stress. Selection under continuous exposure to gradually increasing cobalt stress levels yielded the most resistant cell population to cobalt. However, the resistance was highly heterogeneous within the mutant populations ranging from 3- to 3700-fold survival rate of isolated individuals to 8 mmol l−1 CoCl2 in the most resistant population. Moreover, cobalt-resistant individual colonies were associated with 2–4-times lower intracellular cobalt contents as compared to wild-type, and with cross-resistance to metals such as nickel, zinc, manganese, but not to copper and chromium ions. Contrary to mutants evolved under continuous exposure to cobalt, those isolated by pulse exposure strategy also exhibited resistance to heat shock and hydrogen peroxide stress. Taken together, this study reinforced the fact that evolutionary engineering is useful in selecting strains with very specific phenotypes, and further illustrated the importance of the strategy chosen to isolate the best evolved strain. 相似文献
996.
997.
Elementary mode analysis: a useful metabolic pathway analysis tool for characterizing cellular metabolism 总被引:1,自引:1,他引:0
Cong?T.?Trinh Aaron?Wlaschin Friedrich?SriencEmail author 《Applied microbiology and biotechnology》2009,81(5):813-826
Elementary mode analysis is a useful metabolic pathway analysis tool to identify the structure of a metabolic network that
links the cellular phenotype to the corresponding genotype. The analysis can decompose the intricate metabolic network comprised
of highly interconnected reactions into uniquely organized pathways. These pathways consisting of a minimal set of enzymes
that can support steady state operation of cellular metabolism represent independent cellular physiological states. Such pathway
definition provides a rigorous basis to systematically characterize cellular phenotypes, metabolic network regulation, robustness,
and fragility that facilitate understanding of cell physiology and implementation of metabolic engineering strategies. This
mini-review aims to overview the development and application of elementary mode analysis as a metabolic pathway analysis tool
in studying cell physiology and as a basis of metabolic engineering. 相似文献
998.
Potential natural product discovery from microbes through a diversity-guided computational framework
Eakasit Pacharawongsakda Sunai Yokwai Supawadee Ingsriswang 《Applied microbiology and biotechnology》2009,82(3):579-586
As the occurrence of natural compounds is related to the spatial distribution and evolution of microorganisms for biological
and ecological relevance, the data integration of chemistry, geography, and phylogeny within an analytical framework is needed
to make better decisions on sourcing the microbes for drug discovery. Such a framework should help researcher to decide on
(a) which microorganisms are capable to produce the structurally diverse-bioactive compounds and (b) where those microbes
could be found. Here, we present GIST (Geospatial Integrated Species, sites and bioactive compound relationships Tracking
tool), a computational framework that could describe and compare how the chemical and genetic diversity varied among microbes
in different areas. GIST mainly exploits the measures of bioactive diversity (BD) and phylogenetic diversity (PD), derived
from the branch length of bioactive dendrogram and phylogenetic tree, respectively. Based on BD and PD, our framework could
provide guidance and tools for measuring, monitoring, and evaluating of patterns and changes in biodiversity of microorganisms
to improve the success rate of drug discovery.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
999.
Wanyao Xia Yu-Qing Jin James D. Kretlow Wei Liu Wenlong Ding Hengyun Sun Guangdong Zhou Wenjie Zhang Yilin Cao 《Biotechnology letters》2009,31(5):639-646
TGF-β1 plays a necessary and important role in the induction of chondrogenic differentiation of bone marrow stromal cells
(BMSCs). In this study, porcine BMSCs were infected with a replication-deficient adenovirus expression vector carrying the
hTGF-β1 gene. The transduced BMSCs were cultured as pelleted micromasses in vitro for 21 days, seeded onto disk-shaped PGA
scaffolds for 3 days and subsequently implanted into the subcutaneous tissue of mice. BMSCs transduced with AdhTGF-β1 expressed
and secreted more hTGF-β1 protein in vitro than those of the control group. Histological and immunohistological examination
of the pellets revealed robust chondrogenic differentiation. Tissues made from cells transduced with AdhTGF-β1 exhibited neocartilage
formation after 3 weeks in vivo. The neocartilage occupied 42 ± 5% of the total tissue volume which was significantly greater
than that of the control group. Furthermore, there was extensive staining for sulfated proteoglycans and type II collagen
in the AdhTGF-β1 group compared to controls, and quantification of GAG content showed significantly greater amounts of GAG
in experimental groups. The results demonstrate that transfer of hTGF-β1 into BMSCs via adenoviral transduction can induce
chondrogenic differentiation in vitro and enhance chondrogenesis in vivo. 相似文献
1000.
Simultaneous electricity generation and selenium removal was evaluated in single-chamber microbial fuel cells (MFCs) with
acetate and glucose as carbon sources. Power output was not affected by selenite up to 125 mg l−1 with glucose as substrate. Coulombic efficiencies of MFCs with glucose increased from 25% to 38% at 150 mg Se l−1. About 99% of 50 and 200 mg Se l−1 selenite was removed in 48 and 72 h for MFCs fed with acetate and glucose, respectively, demonstrating the potential of using
MFC technology for Se remediation. 相似文献