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排序方式: 共有306条查询结果,搜索用时 15 毫秒
81.
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83.
Mark E. Schnute Patrick M. O’Brien Joe Nahra Mark Morris W. Howard Roark Cathleen E. Hanau Peter G. Ruminski Jeffrey A. Scholten Theresa R. Fletcher Bruce C. Hamper Jeffery N. Carroll William C. Patt Huey S. Shieh Brandon Collins Alexander G. Pavlovsky Katherine E. Palmquist Karl W. Aston Jeffrey Hitchcock Michael D. Rogers Joseph McDonald Teresa Sunyer 《Bioorganic & medicinal chemistry letters》2010,20(2):576-580
84.
Richard A. Lasher Jeffrey C. Wolchok Monir K. Parikh James P. Kennedy Robert W. Hitchcock 《Biotechnology progress》2010,26(3):857-864
Controlling environmental conditions, such as mechanical stimuli, is critical for directing cells into functional tissue. This study reports on the development of a bioreactor capable of controlling the mechanical environment and continuously measuring force‐displacement in engineered tissue. The bioreactor was built from off the shelf components, modified off the shelf components, and easily reproducible custom built parts to facilitate ease of setup, reproducibility and experimental flexibility. A T‐flask was modified to allow for four tissue samples, mechanical actuation via a LabView controlled stepper motor and transduction of force from inside the T‐flask to an external sensor. In vitro bench top testing with instrumentation springs and tissue culture experiments were performed to validate system performance. Force sensors were highly linear (R2 > 0.998) and able to maintain force readings for extended periods of time. Tissue culture experiments involved cyclic loading of polyurethane scaffolds seeded with and without (control) human foreskin fibroblasts for 8 h/day for 14 days. After supplementation with TGF‐β, tissue constructs showed an increase in stiffness between consecutive days and from the acellular controls. These experiments confirmed the ability of the bioreactor to distinguish experimental groups and monitor tissue stiffness during tissue development. © 2010 American Institute of Chemical Engineers Biotechnol. Prog., 2010 相似文献
85.
Lloyd T.J. Evans F. Geoffrey N. Cloke Peter B. Hitchcock 《Inorganica chimica acta》2010,363(6):1114-147
A series of mono- and bis-amide scandium and yttrium compounds incorporating the furyl-substituted disilazide ligand, [N{SiMe2R}2]− {i} (where R = 2-methylfuryl) have been synthesized. The compounds Sc{i}Cl2 (1), Sc{i}(CH2SiMe3)2 (2) and Sc{i}(OAr)2 (3) were made from suitable scandium starting materials employing either a salt metathesis protocol with Li{i} or via protonolysis of Sc-C bonds by the neutral amine H{i}. The thermally unstable bis-alkyl yttrium compound, ‘Y{i}(CH2SiMe3)2’ was isolated as the bis-THF adduct (4) and the bis-aryloxide Y{i}(OAr)2 (5) was synthesized by elimination of LiOAr from Y(OAr)3. The bis-amide complex Y{i}2Cl (6) and conversion to a rare example of an yttrium benzyl compound Y{i}2(CH2Ph) (7) are described. The yttrium cation, [Y{i}2]+, was synthesized by benzyl abstraction from 7 using B(C6F5)3. Structural characterization of representative examples show variation in the coordination modes for amide ligand {i}, differing primarily in the number of furyl groups that coordinate to the metal, with examples in which zero, one or two M-Ofuryl bonds are present. Preliminary investigation in two areas of catalysis are presented. 相似文献
86.
Rosemary J Redfield Wendy A Findlay Janine Bossé J Simon Kroll Andrew DS Cameron John HE Nash 《BMC evolutionary biology》2006,6(1):82-15
Background
Many bacteria can take up DNA, but the evolutionary history and function of natural competence and transformation remain obscure. The sporadic distribution of competence suggests it is frequently lost and/or gained, but this has not been examined in an explicitly phylogenetic context. Additional insight may come from the sequence specificity of uptake by species such as Haemophilus influenzae, where a 9 bp uptake signal sequence (USS) repeat is both highly overrepresented in the genome and needed for efficient DNA uptake. We used the distribution of competence genes and DNA uptake specificity in H. influenzae 's family, the Pasteurellaceae, to examine the ancestry of competence. 相似文献87.
Repeated evolution of an acetate-crossfeeding polymorphism in long-term populations of Escherichia coli 总被引:1,自引:0,他引:1
Six out of 12 independent replicate populations of Escherichia coli
maintained in long-term glucose-limited continuous culture for up to
approximately 1,750 generations evolve polymorphisms maintained by acetate
crossfeeding. In all cases, the acetate-crossfeeding phenotype is
associated with semiconstitutive overexpression of acetyl CoA synthetase,
which allows for the enhanced uptake of low levels of exogenous acetate.
Mutations in the 5' regulatory region of the acetyl CoA synthetase locus
are responsible for all the acetate crossfeeding phenotypes found. These
changes were either transposable-element insertions or a single T-->A
nucleotide substitution at position -93 relative to the acs gene
translation start site.
相似文献
88.
Morphological heterogeneity among Salmonella lipopolysaccharide chemotypes in silver-stained polyacrylamide gels. 总被引:340,自引:101,他引:239
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The morphological heterogeneity of lipopolysaccharides (LPSs) among salmonella mutants with different LPS chemotypes was analyzed in silver-stained polyacrylamide gels. The biochemical differences in the LPS chemotypes were reflected in the unique profiles of the purified LPSs. The LPS profiles in the whole-cell lysates were also unique for each chemotype. (Whole-cell lysates were assessed by a method which preferentially silver stains LPS and by a proteinase K digest of whole-cell lysates. The silver-stained LPS profiles of proteinase K-digested lysates were similar to the homologous purified LPS and could be used to preliminarily characterize the LPS chemotype before purification.) In summary, biochemical variation in LPS composition can be detected in silver-stained polyacrylamide gels. 相似文献
89.
High-frequency fusion of Streptomyces parvulus or Streptomyces antibioticus protoplasts induced by polyethylene glycol. 总被引:6,自引:0,他引:6
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Conditions were established for the regeneration of protoplasts of Streptomyces parvulus and Streptomyces antibioticus to the mycelial form. Regeneration was accomplished with a hypertonic medium that contained sucrose, CaCl2, MgCl2, and low levels of phosphate. High-frequency fusion of protoplasts derived from auxotrophic strains of S. parvulus or S. antibioticus was induced by polyethylene glycol 4,000 (42%, wt/vol). The frequency of genetic transfer by the fusogenic procedure varied with the auxotrophic strains examined. Fusion with auxotrophic strains of S. parvulus resulted in the formation of true prototrophic recombinants. Similar studies with S. antibioticus revealed that both stable prototrophic recombinants and heterokaryons were formed. 相似文献
90.
Primitive neuroectodermal tumor of the uterus. A case report 总被引:2,自引:0,他引:2
BACKGROUND: Primitive neuroectodermal tumor (PNET) is a rare tumor derived from fetal neuroectodermal cells. These tumors occur in the central nervous system and in peripheral locations. Histologic diagnosis is the standard since most of these tumors are detected at an advanced stage. CASE: A 17-year-old female presented with persistent vaginal bleeding. Physical examination revealed a 4-cm, hard, barrel-shaped cervix. A cervicovaginal smear was obtained. The specimen was hypercellular, with small to medium-sized, round, malignant cells. A diagnosis of PNET was made from the histologic sections of the surgical specimen. CONCLUSION: When numerous small round cells in a diffuse pattern are seen on a Pap smear, the differential diagnosis is long and difficult. However, with careful evaluation of the cytologic features, a few reasonable differential diagnoses can be reached. Furthermore, with liquid-based Pap smears, material is available for immunohistochemical staining to narrow the range even more. Using all resources, including a good clinical history, a cytopathologist can give the clinician an early diagnosis for intervention and treatment. 相似文献