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71.
Ecology of uncultivated Oscillospira species in the rumen of cattle, sheep, and reindeer as assessed by microscopy and molecular approaches 总被引:8,自引:0,他引:8
Mackie RI Aminov RI Hu W Klieve AV Ouwerkerk D Sundset MA Kamagata Y 《Applied and environmental microbiology》2003,69(11):6808-6815
The ecology of the uncultured, but large and morphologically conspicuous, rumen bacterium Oscillospira spp. was studied. Oscillospira-specific 16S rRNA gene sequences were detected in North American domestic cattle, sheep from Australia and Japan, and Norwegian reindeer. Phylogenetic analysis of the sequences obtained allowed definition of three operational taxonomic units within the Oscillospira clade. Consistent with this genetic diversity, we observed atypical smaller morphotypes by using an Oscillospira-specific fluorescence in situ hybridization probe. Despite the visual disappearance of typical large Oscillospira morphotypes, the presence of Oscillospira spp. was still detected by Oscillospira-specific PCR in the rumen of cattle and sheep. These observations suggest the broad presence of Oscillospira species in various rumen ecosystems with the level, and most likely the morphological form, dependent on diet. An ecological analysis based on enumeration of the morphologically conspicuous, large-septate form confirms that the highest counts are associated with the feeding of fresh forage diets to cattle and sheep and in two different subspecies of reindeer investigated. 相似文献
72.
Calcium signalling: dynamics,homeostasis and remodelling 总被引:1,自引:0,他引:1
Ca2+ is a highly versatile intracellular signal that operates over a wide temporal range to regulate many different cellular processes. An extensive Ca2+-signalling toolkit is used to assemble signalling systems with very different spatial and temporal dynamics. Rapid highly localized Ca2+ spikes regulate fast responses, whereas slower responses are controlled by repetitive global Ca2+ transients or intracellular Ca2+ waves. Ca2+ has a direct role in controlling the expression patterns of its signalling systems that are constantly being remodelled in both health and disease. 相似文献
73.
WAVE2 deficiency reveals distinct roles in embryogenesis and Rac-mediated actin-based motility 总被引:11,自引:0,他引:11
Yan C Martinez-Quiles N Eden S Shibata T Takeshima F Shinkura R Fujiwara Y Bronson R Snapper SB Kirschner MW Geha R Rosen FS Alt FW 《The EMBO journal》2003,22(14):3602-3612
The Wiskott-Aldrich syndrome related protein WAVE2 is implicated in the regulation of actin-cytoskeletal reorganization downstream of the small Rho GTPase, Rac. We inactivated the WAVE2 gene by gene-targeted mutation to examine its role in murine development and in actin assembly. WAVE2-deficient embryos survived until approximately embryonic day 12.5 and displayed growth retardation and certain morphological defects, including malformations of the ventricles in the developing brain. WAVE2-deficient embryonic stem cells displayed normal proliferation, whereas WAVE2-deficient embryonic fibroblasts exhibited severe growth defects, as well as defective cell motility in response to PDGF, lamellipodium formation and Rac-mediated actin polymerization. These results imply a non-redundant role for WAVE2 in murine embryogenesis and a critical role for WAVE2 in actin-based processes downstream of Rac that are essential for cell movement. 相似文献
74.
75.
Multiple myeloma (MM) is a neoplasm of a terminally differentiated B-cell. Human myeloma cell lines were shown to be suitable model systems for use in various fields of the biological sciences. Within the last 20 years more than 100 cell lines have been established. So-called 'myeloma cell lines' have been previously reported and are still widely used which are in reality Epstein-Barr virus (EBV)-positive B-lymphoblastoid cell lines. The presence of the EBV-genome in residual normal B-cells provides them with a selective growth advantage after explantation. Cell lines represent an extremely important resource for research in a variety of fields and disciplines. As the cell lines are used as in vitro model systems in lieu of primary material, it is crucial that the cells in the culture flasks faithfully correspond to the purported objects of study. On closer examination, the use of false cell lines may be seen to invalidate a significant percentage of scientific work, or at least cast doubts on the relevance of these in vitro results to the cell type or tumor in vivo. Ultimately, use of cross-contaminated cell lines is a waste of human and material resources. Henceforth, it should be mandatory to prove the proper derivation of each new cell line by comparing DNA fingerprints or karyotypes of the patient's primary cells and the cultured cells. The availability of well characterized and authenticated bona fide MM cell lines is of great importance for the study of the biology, etiology and treatment of the disease. 相似文献
76.
Residual dipolar couplings (RDCs) observed between nuclear spins in molecules in partially oriented media have become a valuable source of information for NMR spectroscopists seeking to structurally characterize biological macromolecules. Examination of the form of the direct (D) and indirect (J) nuclear spin-spin coupling Hamiltonians indicates that all observed RDCs contain an unknown contribution from the anisotropic part of J (J) in addition to the direct dipolar contribution, D
PQ. Here, we evaluate the influence of J on RDCs through a series of DFT calculations on model peptides. Very small corrections to one-bond RDCs measured between heavy atoms in peptides and proteins are recommended: +0.51% for N-C spin pairs, and +0.45% for C-C spin pairs. The corrections to RDCs involving at least one proton are negligible. This latter point is likely to be equally applicable to nucleic acids and oligosaccharides in addition to peptides and proteins. Finally, the orientations of the J(N, C) and J(C, C) tensors in the molecular framework are reported for glycylglycine. 相似文献
77.
Xue CB He X Roderick J Corbett RL Duan JJ Liu RQ Covington MB Qian M Ribadeneira MD Vaddi K Christ DD Newton RC Trzaskos JM Magolda RL Wexler RR Decicco CP 《Bioorganic & medicinal chemistry letters》2003,13(24):4299-4304
Modifications of the lead TACE inhibitor 1 (N-hydroxy-trans-2-[[4-(4-quinolinyloxymethyl)anilinyl]carbonyl]-1-cyclohexanecarboxamide) at the cyclohexyl ring and the quinoline moiety led to the identification of a series of piperidine containing TACE inhibitors with potent activity in the inhibition of TNF-alpha release in the whole blood assay (WBA). The most potent analogue IM491 [N-hydroxy-(5S,6S)-1-methyl-6-[[4-(2-methyl-4-quinolinylmethoxy)anilinyl]carbonyl]-5-piperidinecarboxamide] exhibited an IC(50) value of 20 nM in WBA with excellent selectivity over MMP-1, -2 and -9 and is orally bioavailable with an F value of 43% in beagle dogs. 相似文献
78.
79.
Biological and molecular characterizations of Toxoplasma gondii strains obtained from southern sea otters (Enhydra lutris nereis) 总被引:2,自引:0,他引:2
Cole RA Lindsay DS Howe DK Roderick CL Dubey JP Thomas NJ Baeten LA 《The Journal of parasitology》2000,86(3):526-530
Toxoplasma gondii was isolated from brain or heart tissue from 15 southern sea otters (Enhydra lutris nereis) in cell cultures. These strains were used to infect mice that developed antibodies to T. gondii as detected in the modified direct agglutination test and had T. gondii tissue cysts in their brains at necropsy. Mouse brains containing tissue cysts from 4 of the strains were fed to 4 cats. Two of the cats excreted T. gondii oocysts in their feces that were infectious for mice. Molecular analyses of 13 strains indicated that they were all type II strains, but that they were genetically distinct from one another. 相似文献
80.