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排序方式: 共有454条查询结果,搜索用时 15 毫秒
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Successful infection of the common marmoset (Callithrix jacchus) with human varicella-zoster virus. 总被引:1,自引:0,他引:1 下载免费PDF全文
P J Provost P M Keller F S Banker B J Keech H J Klein R S Lowe D H Morton A H Phelps W J McAleer R W Ellis 《Journal of virology》1987,61(10):2951-2955
The common marmoset, Callithrix jacchus, can be infected with human varicella-zoster virus (VZV), both wild-type strain KMcC and attenuated vaccine strain Oka/Merck. Infection was accomplished with either whole-cell-associated or cell extract VZV by combined oral-nasal-conjunctival application and was characterized by substantial and persistent anti-VZV antibody responses. The infectivity of VZV for marmosets was destroyed by treatment of inocula with heat or UV light. Diluted inocula with as few as 40 PFU/ml were infectious for marmosets. The lungs were demonstrated to be a major site of viral replication; both the presence of viral antigens and signs of pneumonia were demonstrated in lung tissues. Four serial passages of VZV KMcC were carried out in C. jacchus by a process of in vitro isolation and culturing of VZV from infected lung tissue and reapplication of the cultured isolates to fresh animals. The isolated viruses were identified as VZV both serologically and by restriction endonuclease analyses. The C. jacchus infectivity model should prove useful for determining the efficacy of subunit and live recombinant VZV vaccines as well as for the study of zoster. 相似文献
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Epidermal growth factor (EGF) was linked to the toxic A chain of ricin toxin (RTA) to produce an EGF-receptor-specific cytotoxic agent, EGF-RTA. Three EGF-RTA-resistant mutants of the human HeLa cell line were selected. These mutant cell lines are 10-fold to more than 100-fold more resistant to EGF-RTA when compared to HeLa cells. The EGF-RTA-resistant mutants have at least as many EGF receptors as parent cells; the basis for the EGF-RTA-resistant phenotype must be distal to EGF binding. The EGF-RTA-resistant cells are not cross-ressitant to ricin or to diphtheria toxin; their mutant phenotype appears to be EGF specific. The EGF-RTA-resistant mutants are able to internalize and degrade EGF. However, the mutants have altered EGF receptor down-regulation and phorbol 12-tetradecanoate 13-acetate modulation properties. EGF-RTA/ammonium chloride and EGF-RTA/adenovirus co-treatment data suggest that the mutant defect(s) which confers EGF-RTA resistance is either in the endosome or at a step(s) in the intracellular EGF processing pathway between the endosome and the lysosome. 相似文献
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Roxanne M. Broadway D.L. Williams Wendy C. Kain G. E. Harman M. Lorito D.P. Labeda 《Letters in applied microbiology》1995,20(5):271-276
Streptomyces albidoflavus NRRL B-16746 secreted three types of chitinolytic enzymes: N -acetyl-glucosaminidase, chitobiosidase and endochitinase. Optimal activity for all three types of enzymes occurred at pH 4–6; however 55–74% of the chitobiosidase and endochitinase activity was detectable at pH 8–10. Chitobiosidase activity originated from two strongly acidic (pI < 3.0) proteins with molecular mass of 27 kDa and 34 kDa, while endochitinase activity originated from five major acidic proteins (pI 5.1, 5.3, 5.75, 5.8–5.9 and 6.4) with molecular mass of 59, 45, 38.5, 27 and 25.5 kDa. Purified chitobiosidases significantly reduced spore germination and germ tube elongation of Botrytis cinerea and Fusarium oxysporum. Chitinolytic enzymes with significant activity at pH 4–10 may be used, transgenically, to reduce the growth and/or development of a broad spectrum of insects and fungi that are major economic pests. 相似文献
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Roxanne Deslauriers Harold C. Jarrell R.Andrew Byrd Ian C.P. Smith 《Biochemical and biophysical research communications》1980,95(3):1211-1217
studies of have shown that encysting cells release polyphosphate into the encystment medium. Mature cysts contain low levels of polyphosphate, as do vegetative cells. Young cysts (7 days) show detectable levels of nucleotide diphosphates and triphosphate similar to those observed in vegetative cells. Mature cysts (90 days) show only excreted polyphosphate as well as a component which has a chemical shift of a phosphodiester. The inorganic phosphate peak in the cyst shows that the cyst milieu is liquid-like and that the intracellular environment maintains a pH between 6 and 7.5 in the presence of extracellular values from 4 to 9. 相似文献
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Nasser Fardousi Everton Nunes da Silva Roxanne Kovacs Josephine Borghi Jorge O. M. Barreto Sren Rud Kristensen Juliana Sampaio Helena Eri Shimizu Luciano B. Gomes Letícia Xander Russo Garibaldi D. Gurgel Timothy Powell-Jackson 《PLoS medicine》2022,19(7)
BackgroundPay-for-performance (P4P) programmes to incentivise health providers to improve quality of care have been widely implemented globally. Despite intuitive appeal, evidence on the effectiveness of P4P is mixed, potentially due to differences in how schemes are designed. We exploited municipality variation in the design features of Brazil’s National Programme for Improving Primary Care Access and Quality (PMAQ) to examine whether performance bonuses given to family health team workers were associated with changes in the quality of care and whether the size of bonus mattered.Methods and findingsFor this quasi-experimental study, we used a difference-in-differences approach combined with matching. We compared changes over time in the quality of care delivered by family health teams between (bonus) municipalities that chose to use some or all of the PMAQ money to provide performance-related bonuses to team workers with (nonbonus) municipalities that invested the funds using traditional input-based budgets. The primary outcome was the PMAQ score, a quality of care index on a scale of 0 to 100, based on several hundred indicators (ranging from 598 to 660) of health care delivery. We did one-to-one matching of bonus municipalities to nonbonus municipalities based on baseline demographic and economic characteristics. On the matched sample, we used ordinary least squares regression to estimate the association of any bonus and size of bonus with the prepost change over time (between November 2011 and October 2015) in the PMAQ score. We performed subgroup analyses with respect to the local area income of the family health team. The matched analytical sample comprised 2,346 municipalities (1,173 nonbonus municipalities; 1,173 bonus municipalities), containing 10,275 family health teams that participated in PMAQ from the outset. Bonus municipalities were associated with a 4.6 (95% CI: 2.7 to 6.4; p < 0.001) percentage point increase in the PMAQ score compared with nonbonus municipalities. The association with quality of care increased with the size of bonus: the largest bonus group saw an improvement of 8.2 percentage points (95% CI: 6.2 to 10.2; p < 0.001) compared with the control. The subgroup analysis showed that the observed improvement in performance was most pronounced in the poorest two-fifths of localities. The limitations of the study include the potential for bias from unmeasured time-varying confounding and the fact that the PMAQ score has not been validated as a measure of quality of care.ConclusionsPerformance bonuses to family health team workers compared with traditional input-based budgets were associated with an improvement in the quality of care.Nasser Fardousi and colleagues investigate the association between performance bonuses and the quality of primary health care delivered by family health teams in Brazil. 相似文献
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Margreet J. Oosterkamp Teun Veuskens Flávia Talarico Saia Sander A. B. Weelink Lynne A. Goodwin Hajnalka E. Daligault David C. Bruce John C. Detter Roxanne Tapia Cliff S. Han Miriam L. Land Loren J. Hauser Alette A. M. Langenhoff Jan Gerritse Willem J. H. van Berkel Dietmar H. Pieper Howard Junca Hauke Smidt Gosse Schraa Mark Davids Peter J. Schaap Caroline M. Plugge Alfons J. M. Stams 《PloS one》2013,8(6)
The genomes of the Betaproteobacteria Alicycliphilus denitrificans strains BC and K601T have been sequenced to get insight into the physiology of the two strains. Strain BC degrades benzene with chlorate as electron acceptor. The cyclohexanol-degrading denitrifying strain K601T is not able to use chlorate as electron acceptor, while strain BC cannot degrade cyclohexanol. The 16S rRNA sequences of strains BC and K601T are identical and the fatty acid methyl ester patterns of the strains are similar. Basic Local Alignment Search Tool (BLAST) analysis of predicted open reading frames of both strains showed most hits with Acidovorax sp. JS42, a bacterium that degrades nitro-aromatics. The genomes include strain-specific plasmids (pAlide201 in strain K601T and pAlide01 and pAlide02 in strain BC). Key genes of chlorate reduction in strain BC were located on a 120 kb megaplasmid (pAlide01), which was absent in strain K601T. Genes involved in cyclohexanol degradation were only found in strain K601T. Benzene and toluene are degraded via oxygenase-mediated pathways in both strains. Genes involved in the meta-cleavage pathway of catechol are present in the genomes of both strains. Strain BC also contains all genes of the ortho-cleavage pathway. The large number of mono- and dioxygenase genes in the genomes suggests that the two strains have a broader substrate range than known thus far. 相似文献
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Daniel C. B. Jeffery Brandon A. Wyse Muhammad Attiq Rehman Geoffrey W. Brown Zhiying You Roxanne Oshidari Hisao Masai Krassimir Y. Yankulov 《Nucleic acids research》2013,41(18):8475-8488
Position-effect variegation (PEV) phenotypes are characterized by the robust multigenerational repression of a gene located at a certain locus (often called gene silencing) and occasional conversions to fully active state. Consequently, the active state then persists with occasional conversions to the repressed state. These effects are mediated by the establishment and maintenance of heterochromatin or euchromatin structures, respectively. In this study, we have addressed an important but often neglected aspect of PEV: the frequency of conversions at such loci. We have developed a model and have projected various PEV scenarios based on various rates of conversions. We have also enhanced two existing assays for gene silencing in Saccharomyces cerevisiae to measure the rate of switches from repressed to active state and vice versa. We tested the validity of our methodology in Δsir1 cells and in several mutants with defects in gene silencing. The assays have revealed that the histone chaperone Chromatin Assembly Factor I is involved in the control of epigenetic conversions. Together, our model and assays provide a comprehensive methodology for further investigation of epigenetic stability and position effects. 相似文献