Method to determine effect of antibiotics at residue levels on R-factor transfer     

M S Brady  S E Katz 《Journal of the Association of Official Analytical Chemists》1988,71(2):299-301

An analytical system was developed which can assess the ability of antibiotic/antimicrobial residues (0.01-1.00 ppm) to affect the conjugal transfer of resistance among the Enterobacteriaceae. The donor strain, Escherichia coli RP-4 (Amr Tcr Nmr Kmr Lac+), and recipient strain, E. coli Sc-8632 (Smr Lac-), were incubated together in a 1:9 donor:recipient ratio for 18 h with gentle shaking (50 rpm) in brain heart infusion broth in the presence of residue levels of antibiotics. The mating cultures were serially diluted and spread-plated onto MacConkey agar containing 25 micrograms streptomycin/mL to select the total recipient population of sensitive E. coli Sc-8632 and transconjugants. After an 18 h incubation at 37 degrees C, the plates were replicated onto MacConkey agar containing 25 micrograms ampicillin/mL to select the ampicillin-resistant transconjugant population. Repeatability was good; the average transfer was 51.8%, with a coefficient of variation of 9.3%. Residue levels of tylosin (0.10 and 1.00 ppm) increased the transfer of the ampicillin marker beyond the 95% confidence limits. Oxytetracycline, bacitracin, streptomycin, penicillin, and virginiamycin did not increase the percent transfer. Oxytetracycline at 0.01 ppm decreased the percent transfer. In general, residue levels of antibiotics (0.01-1.00 ppm) did not affect the conjugal transfer of antibiotic resistance.  相似文献   

Turbidimetric assay for tetracyclines in feeds using a microtiter plate system     

M S Brady  S E Katz 《Journal of the Association of Official Analytical Chemists》1991,74(3):465-470

The microtiter plate system for turbidimetric assay of chlortetracycline (CTC) and oxytetracycline (OTC) levels in feeds uses a 96 well microtiter plate, a multichannel pipette, and an ELISA reader to measure turbidity. Feeds are extracted for both tetracyclines using AOAC extraction systems. For CTC, the range of the standard curve is 0.001-0.005 microgram CTC/mL; for OTC, the range is 0.004-0.016 microgram OTC/mL. Repeatability of CTC assays, as shown by the coefficient of variation (CV), ranged from 0.54 to 5.65% for same-day assays and from 2.01 to 9.39% for assays on different days. For OTC, CVs ranged from 2.69 to 10.01% for same-day assays and 3.24 to 9.08% for different-day assays. Average recoveries for CTC were 108.7% for same-day assays and 106.8% for different-day assays; for OTC, average recoveries were 112.4% and 106.5% for same-day and different-day assays, respectively.  相似文献   

Forest disturbance and river proximity influence chameleon abundance in Madagascar     

Richard K.B. Jenkins  Lee D. Brady  Jeanneney Rabearivony 《Biological conservation》2003,109(3):407-415

Many chameleon species are thought to be restricted to primary rainforest where they are threatened by the continued fragmentation and degradation of natural vegetation. We surveyed chameleon abundance in forest subject to high disturbance, low disturbance and in a riparian zone in Madagascar. Four Calumma species and Brookesia thieli were present in all habitats, but B. minima was not recorded from the high-disturbance forest. Chameleons were more abundant in rainforest subject to low-disturbance (e.g. selective timber extraction) than in patches of high-disturbance forest that was recovering from burning. Riparian zones within low-disturbance forest provided linear patches of high chameleon abundance and are therefore an important conservation resource because they also protect a range of other endemic and threatened species. Carefully designed management plans are needed to conserve biodiversity and allow the sustainable use of forest products by people in Madagascar.  相似文献   

Cell identity mediates the response of Arabidopsis roots to abiotic stress   总被引：1，自引：0，他引：1  

Dinneny JR  Long TA  Wang JY  Jung JW  Mace D  Pointer S  Barron C  Brady SM  Schiefelbein J  Benfey PN 《Science (New York, N.Y.)》2008,320(5878):942-945

  相似文献   

Biomass recalcitrance: engineering plants and enzymes for biofuels production   总被引：5，自引：0，他引：5  

Himmel ME  Ding SY  Johnson DK  Adney WS  Nimlos MR  Brady JW  Foust TD 《Science (New York, N.Y.)》2007,315(5813):804-807

Lignocellulosic biomass has long been recognized as a potential sustainable source of mixed sugars for fermentation to biofuels and other biomaterials. Several technologies have been developed during the past 80 years that allow this conversion process to occur, and the clear objective now is to make this process cost-competitive in today's markets. Here, we consider the natural resistance of plant cell walls to microbial and enzymatic deconstruction, collectively known as "biomass recalcitrance." It is this property of plants that is largely responsible for the high cost of lignocellulose conversion. To achieve sustainable energy production, it will be necessary to overcome the chemical and structural properties that have evolved in biomass to prevent its disassembly.  相似文献   

Sex stimulant and attractant in the Indian meal moth and in the almond moth     

Brady UE  Tumlinson JH  Brownlee RG  Silverstein RM 《Science (New York, N.Y.)》1971,171(3973):802-804

cis-9, trans-12-Tetradecadien-1-yl acetate was isolated from the female Indian meal moth, Plodia interpunctella (Hübner), and the female almond moth, Cadra cautella (Walker). It is the major if not the sole component of the sex stimulatory and attractant pheromone of female Plodia. It is present in the pheromone of the female Cadra along with at least one synergist.  相似文献   

Projective imaging of pulsatile flow with magnetic resonance   总被引：8，自引：0，他引：8  

V J Wedeen  R A Meuli  R R Edelman  S C Geller  L R Frank  T J Brady  B R Rosen 《Science (New York, N.Y.)》1985,230(4728):946-948

Noninvasive angiography with magnetic resonance is demonstrated. Signal arising in all structures except vessels that carry pulsatile flow is eliminated by means of velocity-dependent phase contrast, electrocardiographic gating, and image subtraction. Background structures become in effect transparent, enabling the three-dimensional vascular tree to be imaged by projection to a two-dimensional image plane. Image acquisition and processing are accomplished with entirely conventional two-dimensional Fourier transform magnetic resonance imaging techniques. When imaged at 0.6 tesla, vessels 1 to 2 millimeters in diameter are routinely detected in a 50-centimeter field of view with data acquisition times less than 15 minutes. Studies of normal and pathologic anatomy are illustrated in human subjects.  相似文献   

DISTRIBUTION OF RADIOACTIVE ARSENIC FOLLOWING INTRAPERITONEAL INJECTION OF SODIUM ARSENITE INTO COTTON RATS INFECTED WITH LITOMOSOIDES CARINII     

Lawton AH  Ness AT  Brady FJ  Cowie DB 《Science (New York, N.Y.)》1945,102(2640):120-122

  相似文献   

Agricultural research and u.s. Trade     

Brady NC 《Science (New York, N.Y.)》1985,230(4725):499

  相似文献   

SPORE series winner. The periodic table of videos     

Haran B  Poliakoff M 《Science (New York, N.Y.)》2011,332(6033):1046-1047

  相似文献