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991.
992.
993.
Recent work on cell division and chromosome orientation and partitioning in Bacillus subtilis has provided insights into cell cycle regulation during growth and development. The cell cycle is an integral part of development and entrance into sporulation is modulated by signals that transmit the status of DNA integrity, chromosome replication and segregation. In addition, B. subtilis modifies cell division and DNA segregation to establish cell-type-specific gene expression during sporulation. 相似文献
994.
Spaceflight and development of immune responses 总被引:1,自引:0,他引:1
Sonnenfeld Gerald; Foster Mareva; Morton Darla; Bailliard Frederique; Fowler Nina A.; Hakenewerth Anne M.; Bates Roge; Miller Edwin S. Jr. 《Journal of applied physiology》1998,85(4):1429-1433
The NIH.R1 Space Shuttle experiment wasdesigned to study the effects of spaceflight on rodent development.Pregnant rats were flown on the Space Shuttle for 11 days, and pregnantcontrol rats were maintained in animal enclosure modules in aground-based chamber under conditions approximating those in flight.Additional controls were in standard housing. The effects of the flighton immunological parameters of dams, fetuses, and pups were determined. Blastogenesis of spleen cells in response to mitogen was inhibited inflown dams but was not inhibited in cells from their pups. Interferon- production by spleen cells showed a trend toward inhibition in flown dams but not in their pups. The response of bonemarrow cells to colony-stimulating factor showed a trend towardinhibition after spaceflight in dams, but the response of fetus and pupliver cells was not inhibited. Total serum IgG was not affected byspaceflight. None of the examined immune parameters that were alteredin rat dams after spaceflight was found to be altered in theiroffspring. 相似文献
995.
Jo Anne Schneider 《Anthropology & education quarterly》1998,29(1):130-132
Growing Up African American in Catholic Schools. Jacqueline Jordan Irvine and Michele Foster, eds. New York: Teachers College Press, 1996. 相似文献
996.
997.
Jarrige A Bréchemier-Baey D Mathy N Duché O Portier C 《Journal of molecular biology》2002,321(3):397-409
Polynucleotide phosphorylase (PNPase), a homotrimeric exoribonuclease present in bacteria, is involved in mRNA degradation. In Escherichia coli, expression of this enzyme is autocontrolled at the translational level. We introduced about 30 mutations in the pnp gene by site-directed mutagenesis, most of them in phylogenetically conserved residues, and determined their effects on the three catalytic activities of PNPase, phosphorolysis, polymerisation and phosphate exchange, as well as on the efficiency of translational repression. The data are presented and discussed in the light of the crystallographic structure of PNPase from Streptomyces antibioticus. The results show that both PNPase activity and the presence of the KH and S1 RNA-binding domains are required for autocontrol. Deletions of these RNA-binding domains do not abolish any of the three catalytic activities, indicating that they are contained in a domain independent of the catalytic centre. Moreover, the catalytic centre was located around the tungsten-binding site identified by crystallography. Some mutations affect the three catalytic activities differently, an observation consistent with the presence of different subsites. 相似文献
998.
The aim of this review is to describe an in vivo assay of the interactions taking place in the Tol-Pal or TonB-ExbB-ExbD envelope complexes in the periplasm of Escherichia coli and between them and colicins or g3p protein of filamentous bacteriophages. Domains of colicins or periplasmic soluble domains of Tol or TonB proteins can be artificially addressed to the periplasm of bacteria by fusing them to a signal sequence from an exported protein. These domains interact specifically in the periplasm with the Tol or TonB complexes and disturb their function, which can be directly detected by the appearance of specific tol or tonB phenotypes. This technique can be used to detect new interactions, to characterize them biochemically and to map them or to induce tol or tonB phenotypes to study the functions of these two complexes. 相似文献
999.
Transposon Mutagenesis and Excision of R′ Plasmids by Conjugative, Chimeric Plasmid pUW942 in Extra-Slow-Growing Rhizobium japonicum Strains 下载免费PDF全文
Transposons Tn501 (specifying mercury resistance) and Tn7 (specifying resistance to trimethoprim and streptomycin) were introduced into extra-slow-growing Rhizobium japonicum by conjugal transfer of the 82 kilobase chimeric plasmid pUW942. Mercury-resistant transconjugants were obtained at a frequency of 10−7 to 10−9. The transfer frequency of streptomycin resistance was lower than that of mercury resistance, and Tn7 was relatively unstable. pUW942 was not maintained as an autonomously replicating plasmid in R. japonicum strains. However, some of the Hgr transconjugants from the RJ19FY, RJ17W, and RJ12S strains acquired antibiotic markers of the vector plasmid pUW942. Southern hybridization of plasmid and chromosomal DNA of R. japonicum strains with 32P-labeled pUW942 and pAS8Rep-1, the same plasmid as pUW942 except that it does not contain Tn501, revealed the formation of cointegrates between pUW942 and the chromosome of R. japonicum. More transconjugants with only Tn501 insertions in plasmids or the chromosome were obtained in crosses with strains RJ19FY and RJ17W than with RJ12S. These retained stable Hgr both in plant nodules and under nonselective in vitro growth conditions. One of the RJ19FY and two of the RJ12S Hgr transconjugants with vector plasmid-chromosome cointegrates conjugally transferred plasmids of 82, 84 or 86, and 90 kilobases, respectively, into plasmidless Escherichia coli C. These plasmids strongly hybridized to pUW942 and EcoRI digests of total DNA of each respective R. japonicum strain but not to indigenous plasmid DNA of the R. japonicum strains. These R′ plasmids consisted of pUW942-specific EcoRI fragments and an additional one or two new fragments derived from the R. japonicum chromosome. 相似文献
1000.
Smith AN Muffley LA Bell AN Numhom S Hocking AM 《Journal of cellular physiology》2012,227(9):3225-3233
Mesenchymal stem cells (MSC) represent emerging cell-based therapies for diabetes and associated complications. Ongoing clinical trials are using exogenous MSC to treat type 1 and 2 diabetes, cardiovascular disease and non-healing wounds due to diabetes. The majority of these trials are aimed at exploiting the ability of these multipotent mesenchymal stromal cells to release soluble mediators that reduce inflammation and promote both angiogenesis and cell survival at sites of tissue damage. Growing evidence suggests that MSC secretion of soluble factors is dependent on tissue microenvironment. Despite the contribution of fatty acids to the metabolic environment of type 2 diabetes, almost nothing is known about their effects on MSC secretion of growth factors and cytokines. In this study, human bone marrow-derived MSC were exposed to linoleic acid, an omega-6 polyunsaturated fatty acid, or oleic acid, a monounsaturated fatty acid, for seven days in the presence of 5.38 mM glucose. Outcomes measured included MSC proliferation, gene expression, protein secretion and chemotaxis. Linoleic and oleic acids inhibited MSC proliferation and altered MSC expression and secretion of known mediators of angiogenesis. Both unsaturated fatty acids induced MSC to increase secretion of interleukin-6, VEGF and nitric oxide. In addition, linoleic acid but not oleic acid induced MSC to increase production of interleukin-8. Collectively these data suggest that exposure to fatty acids may have functional consequences for MSC therapy. Fatty acids may affect MSC engraftment to injured tissue and MSC secretion of cytokines and growth factors that regulate local cellular responses to injury. 相似文献