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排序方式: 共有171条查询结果,搜索用时 15 毫秒
81.
Simultaneous determination of fluoroquinolones and tetracyclines in chicken muscle using HPLC with fluorescence detection 总被引:2,自引:0,他引:2
Schneider MJ Braden SE Reyes-Herrera I Donoghue DJ 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》2007,846(1-2):8-13
A multiresidue method has been developed which allows for the simultaneous determination of both fluoroquinolones and tetracyclines in chicken muscle. Samples were extracted with a mix of acetonitrile and 0.1 M citrate, 150 mM MgCl(2), pH 5.0. After centrifugation and evaporation, the extracts could be analyzed by liquid chromatography with fluorescence detection. Good recoveries (63-95%) were obtained from samples fortified with a mix of five fluoroquinolones and three tetracyclines, with satisfactory relative standard deviations. Limits of detection were 0.5 ng/g (danofloxacin), 1 ng/g (oxytetracycline, ciprofloxacin, enrofloxacin), 1.5 ng/g (tetracycline), 2 ng/g (difloxacin) and 5 ng/g (sarafloxacin, chlortetracycline). Enrofloxacin and its metabolite ciprofloxacin, as well as oxytetracycline were determined in enrofloxacin and oxytetracycline incurred chicken muscle using this method. 相似文献
82.
Transcriptional recapitulation and subversion of embryonic colon development by mouse colon tumor models and human colon cancer
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Kaiser S Park YK Franklin JL Halberg RB Yu M Jessen WJ Freudenberg J Chen X Haigis K Jegga AG Kong S Sakthivel B Xu H Reichling T Azhar M Boivin GP Roberts RB Bissahoyo AC Gonzales F Bloom GC Eschrich S Carter SL Aronow JE Kleimeyer J Kleimeyer M Ramaswamy V Settle SH Boone B Levy S Graff JM Doetschman T Groden J Dove WF Threadgill DW Yeatman TJ Coffey RJ Aronow BJ 《Genome biology》2007,8(7):R131-26
83.
Many organism behaviors are innate or instinctual and have been “hard-coded” through evolution. Current approaches to understanding these behaviors model evolution as an optimization problem in which the traits of organisms are assumed to optimize an objective function representing evolutionary fitness. Here, we use a mechanistic birth-death dynamics approach to study the evolution of innate behavioral strategies in a simulated population of organisms. In particular, we performed agent-based stochastic simulations and mean-field analyses of organisms exploring random environments and competing with each other to find locations with plentiful resources. We find that when organism density is low, the mean-field model allows us to derive an effective objective function, predicting how the most competitive phenotypes depend on the exploration-exploitation trade-off between the scarcity of high-resource sites and the increase in birth rate those sites offer organisms. However, increasing organism density alters the most competitive behavioral strategies and precludes the derivation of a well-defined objective function. Moreover, there exists a range of densities for which the coexistence of many phenotypes persists for evolutionarily long times. 相似文献
84.
Ectopic DICER-LIKE1 expression in P1/HC-Pro Arabidopsis rescues phenotypic anomalies but not defects in microRNA and silencing pathways 总被引:1,自引:0,他引:1
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Mlotshwa S Schauer SE Smith TH Mallory AC Herr JM Roth B Merchant DS Ray A Bowman LH Vance VB 《The Plant cell》2005,17(11):2873-2885
Expression of the viral silencing suppressor P1/HC-Pro in plants causes severe developmental anomalies accompanied by defects in both short interfering RNA (siRNA) and microRNA (miRNA) pathways. P1/HC-Pro transgenic lines fail to accumulate the siRNAs that mediate RNA silencing and are impaired in both miRNA processing and function, accumulating abnormally high levels of miRNA/miRNA* processing intermediates as well as miRNA target messages. Both miRNA and RNA silencing pathways require participation of DICER-LIKE (DCL) ribonuclease III-like enzymes. Here, we investigate the effects of overexpressing DCL1, one of four Dicers in Arabidopsis thaliana, on P1/HC-Pro-induced defects in development and small RNA metabolism. Expression of a DCL1 cDNA transgene (35S:DCL1) produced a mild gain-of-function phenotype and largely rescued dcl1 mutant phenotypes. The 35S:DCL1 plants were competent for virus-induced RNA silencing but were impaired in transgene-induced RNA silencing and in the accumulation of some miRNAs. Ectopic DCL1 largely alleviated developmental anomalies in P1/HC-Pro plants but did not correct the P1/HC-Pro-associated defects in small RNA pathways. The ability of P1/HC-Pro plants to suppress RNA silencing and the levels of miRNAs, miRNA*s, and miRNA target messages in these plants were essentially unaffected by ectopic DCL1. These data suggest that P1/HC-Pro defects in development do not result from general impairments in small RNA pathways and raise the possibility that DCL1 participates in processes in addition to miRNA biogenesis. 相似文献
85.
Michael Aide Donn Beighley Indi Braden David Mauk Wesley Mueller Sven Svenson 《Soil & Sediment Contamination》2013,22(2):132-150
A critical need exists for data evaluation protocols to determine if heavy metal deposition has impacted soil or sediment. For routine reconnaissance these protocols need to be analytically precise and affordable, two issues lacking in many regions. We employed a low-cost, commercially available aqua regia digestion procedure and developed a simple protocol for isolating pristine soil horizons and conservative indexing elements to compare to more Pb impacted soil horizons. Strongly Pb impacted soil horizons are easy to ascertain; however, moderately to slightly Pb impacted soils are more problematic to identify because of the natural Pb variation in soils. Using the harmonic mean of the soil concentrations of Lanthanum (La) and Neodymium (Nd) and also the soil concentrations of Thorium (Th) as conservative indexing elements, we were able to discriminate pristine soils from slightly to moderately Pb impacted soils. Ro values are estimators of elemental gain and loss, with Ro values greater than unity implying Pb addition, providing the comparative loss of other elements or biocycling are substantial contributing factors. All pedons known to have received Pb from atmospheric addition exhibited Ro values appreciably greater than unity, whereas soils known to be not impact or at most minimally impacted showed Ro values near unity. Commercially available and relative low cost aqua regia digestion analysis provided the analytical data for Pb, Fe, La, Nd and Th. 相似文献
86.
J. C. Rutledge K. T. Cain L. A. Hughes P. W. Braden W. M. Generoso 《Mutation research》1986,163(3):299-302
Unbalanced (duplication/deficiency) sperm from balanced reciprocal translocations induced in spermatogonial stem cells of mice generally lead to embryonic lethality around the time of implantation. In a recent study (Generoso et al., 1985), it was found that the incidence of X-ray-induced embryonic lethality differed markedly between two hybrid stocks of irradiated male mice. A parallel difference in the frequencies of reciprocal translocations was observed cytologically in the meiocytes of irradiated males. In the present report, which is an adjunct to the study by Generoso et al. (1985), it was determined whether or not similar differences between the two stocks exist for congenital defects resulting from genetic damage to stem-cell spermatogonia. The results indicate not only an association between the frequencies of induced reciprocal translocations and congenital abnormalities, but also a parallel greater frequency of induced malformations in the (C3H × 101)F1 stock versus the (SEC × C57BL)F1 stock of males. 相似文献
87.
88.
David J. Moore Mollie J. P. Roediger Lynn E. Eberly Kaitlin Blackstone Braden Hale Amy Weintrob Anuradha Ganesan Brian K. Agan Scott L. Letendre Nancy F. Crum-Cianflone 《PloS one》2012,7(11)
Background
HIV-associated neurocognitive disorders (HAND) remain prevalent despite improved antiretroviral treatment (ART), and it is essential to have a sensitive and specific HAND screening tool.Methods
Participants were 200 HIV-infected US military beneficiaries, managed early in the course of HIV infection, had few comorbidities, and had open access to ART. Participants completed a comprehensive, seven-domain (16-test), neuropsychological battery (∼120 min); neurocognitive impairment (NCI) was determined using a standardized score derived from demographically adjusted T-scores (global deficit score ≥0.5). Restricting the estimated administration time of the screening battery to < = 20 minutes, we examined the sensitivity and specificity of detecting NCI for all possible combinations of 2-, 3-, and 4- tests from the comprehensive battery.Results
Participants were relatively healthy (median CD4 count: 546 cells/mm3) with 64% receiving ART. Prevalence of NCI was low (19%). The best 2-test screener included the Stroop Color Test and the Hopkins Verbal Learning Test-Revised (11 min; sensitivity = 73%; specificity = 83%); the best 3-test screener included the above measures plus the Paced Auditory Serial Addition Test (PASAT; 16 min; sensitivity = 86%; specificity = 75%). The addition of Action Fluency to the above three tests improved specificity (18 min; sensitivity = 86%; specificity = 87%).Conclusions
Combinations of widely accepted neuropsychological tests with brief implementation time demonstrated good sensitivity and specificity compared to a time intensive neuropsychological test battery. Tests of verbal learning, attention/working memory, and processing speed are particularly useful in detecting NCI. Utilizing validated, easy to administer, traditional neuropsychological tests with established normative data may represent an excellent approach to screening for NCI in HIV. 相似文献89.
90.
Double-stranded RNA binding domain (dsRBD) containing proteins are critical components of the microRNA (miRNA) pathway, with key roles in small RNA biogenesis, modification, and regulation. DiGeorge Critical Region 8 (DGCR8) is a 773 amino acid, dsRBD-containing protein that was originally identified in humans as a protein encoded in the region of chromosome 22 that is deleted in patients with DiGeorge syndrome. Now, it is realized that DGCR8 complements the nuclear RNase III Drosha to initiate miRNA biogenesis by promoting efficient recognition and cleavage of primary miRNAs (pri-miRNA). A pair of C-terminal tandem dsRBDs separated by a flexible linker are required for pri-miRNA substrate binding and recognition. The crystal structure of the DGCR8 core region comprising residues 493–720 revealed that each dsRBD adopts the canonical αβββα fold. However, several residues located in important flexible regions including the β1-β2-loop implicated in canonical dsRNA recognition are absent in the crystal structure and no RNA-bound structure of DGCR8 has been reported. Here we report the 1HN, 13C, and 15N backbone resonance assignments of the 24 kDa, 214 amino acid human DGCR8core (residues 493–706) by heteronuclear NMR spectroscopy. Our assignments lay the foundation for a detailed solution state characterization of the dynamical and RNA-binding properties of this protein in solution. 相似文献