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151.
Holliday structure resolving enzyme endonuclease VII (endo VII) of phage T4 is highly toxic for E. coli when expressed outside of the phage infection environment. As a consequence, plasmids with a mutated gene 49, the gene which encodes for endo VII, can be easily isolated and characterised. We have isolated and characterised 400 survivors from independent transformations with a plasmid carrying gene 49 under the control of the T7 promoter. The majority had mutated gene 49 by IS10 insertions which almost exclusively mapped to a distinct site. When this site was mutated other insertion sites were observed as well as an increase in other mutational events including large deletions. Neither of the observed insertion sites mapped matched the consensus IS10 sequence completely. Additionally when the level of expression of gene 49 was altered the distribution of mutations was changed suggesting that other elements apart from the target sequence are necessary for determining IS10 insertion. The expression of gene 49 in E. coli provides a particularly useful tool for the analysis of mutational events. 相似文献
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153.
Chemically modified low density lipoproteins as inducers of enzyme release from macrophages 总被引:1,自引:0,他引:1
Macrophages carry receptors on their surface for acetylated low density lipoprotein (ac-LDL). Receptor-mediated endocytosis of ac-LDL is followed by intracellular cholesterol accumulation. We investigated whether occupation of these binding sites evokes the release of hydrolytic enzymes from mouse peritoneal macrophages cultured for up to 48 h. ac-LDL at concentrations ranging from 25-250 micrograms protein/ml was noted to promote in a dose-dependent fashion secretion of the neutral proteinase elastase (EC 3.4.21.37) and the lysosomal acid hydrolases N-acetyl-beta-glucosaminidase (EC 3.2.1.30), beta-glucuronidase (EC 3.2.1.31), beta-galactosidase (EC 3.2.1.23), alpha-mannosidase (EC 3.2.1.24) and cathepsin D (EC 3.4.23.5). This stimulatory effect was non-cytotoxic. LDL modified by treatment with malondialdehyde was also capable of augmenting enzyme liberation into culture supernates. These findings may have implications for some aspects of the atherosclerotic process. 相似文献
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155.
From 1998 to 2001 a total of about 1172 conventionally and organically produced samples of wheat, rye, barley and triticale were examined for the presence of deoxynivalenol (DON) and zearalenone (ZON). Furthermore, feedstuffs for pigs were included in the monitoring of Fusarium toxins. DON and ZON analyses were performed using ELISA or HPLC. The incidences and levels of toxins varied from year to year. Overall contamination levels were highest in wheat and triticale, followed by rye and barley. The highest DON contaminations were found in 1998. The probes of the years 1999-2001 showed lower incidences of Fusarium toxins. The second examined mycotoxin ZON was detected at lower levels in cereals. Similar results were observed in the monitoring of feedstuffs. 相似文献
156.
Summary Light promotes the acropetal movement of 2-[14C]ABA through root segments of Phaseolus coccineus L. The promotion occurs only when the segments are irradited during the transport period. Red light and blue light are as effective as white light. There is no significant promotion when the segments are irradiated with green light or when they are kept in darkness during the transport period after preceding light treatment. Light has no effect on basipetal ABA-transport.
Abkürzungen ABA Abscisinsäure - D Dunkel - GA Gibberellinsäure - IAA Indolessigsäure - L Licht - PPO Diphenyloxazol 相似文献
Abkürzungen ABA Abscisinsäure - D Dunkel - GA Gibberellinsäure - IAA Indolessigsäure - L Licht - PPO Diphenyloxazol 相似文献
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158.
Kathleen Regan Claudia Kammann Karin Hartung Katharina Lenhart Christoph Müller Laurent Philippot Ellen Kandeler Sven Marhan 《Global Change Biology》2011,17(10):3176-3186
Long‐term effects of elevated atmospheric CO2 on the ammonia‐oxidizing and denitrifying bacteria in a grassland soil were investigated to test whether a shift in abundance of these N‐cycling microorganisms was responsible for enhanced N2O emissions under elevated atmospheric CO2. Soil samples (7.5 cm increments to 45 cm depth) were collected in 2008 from the University of Giessen Free Air Carbon dioxide Enrichment (GiFACE), a permanent grassland exposed to moderately elevated atmospheric CO2 (+20%) since 1998. GiFACE plots lay on a soil moisture gradient because of gradually changing depth to the underlying water table and labeled as the DRY block (furthest from water table), MED block (intermediate to water table), and WET block (nearest to water table). Mean N2O emissions measured since 1998 have been significantly higher under elevated CO2. This study sought to identify microbial and biochemical parameters that might explain higher N2O emissions under elevated CO2. Soil biochemical parameters [extractable organic carbon (EOC), dissolved organic nitrogen (DON), NH4+, NO3?], and abundances of genes encoding the key enzymes involved in ammonia oxidation (amoA) and denitrification (nirK, nirS, nosZ) depended more on soil depth and block (underlying soil moisture gradient) than on elevated CO2. Ammonia oxidation and denitrification gene abundances, relative abundances (ratios) of nirS to nirK, of nosZ to both nirS and to nirK, and of the measured soil biochemical properties DON and NO3? tended to be lower in elevated CO2 plots as compared with ambient plots in the MED and WET blocks while the DRY block exhibited an opposite trend. High N2O emissions under elevated CO2 in the MED and WET blocks correlated with lower nosZ to nirK ratios, suggesting that increased N2O emissions under elevated CO2 might be caused by a higher proportion of N2O‐producing rather than N2O consuming (N2 producing) denitrifiers. 相似文献
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160.
Katrine Hartung Hansen Peter Damborg Margit Andreasen S?ren Saxmose Nielsen Luca Guardabassi 《Applied and environmental microbiology》2013,79(3):794-798
Current knowledge on extended-spectrum beta-lactamases (ESBLs) in animals is based largely on cross-sectional studies and qualitative data. The aim of this longitudinal study was to elucidate carriage proportions and fecal counts of ESBL-producing Escherichia coli in pigs during the production cycle. At each of three ESBL-positive single-sited farrow-to-finisher pig farms (farms A, B, and C) included in the study, individual fecal samples were taken from 17 to 20 sows 1 week before farrowing and from 2 piglets of each sow''s litter four times from birth to slaughter (as piglets, weaners, and finishers). Cefotaxime (CTX)-resistant coliforms in feces were counted on MacConkey agar containing 2 μg/ml CTX and characterized for the presence of ESBL-encoding genes by PCR and sequencing. CTX-M-positive pigs were detected in all age groups at farms A (blaCTX-M-9 group, compatible with blaCTX-M-14/17) and B (blaCTX-M-1 group, compatible with blaCTX-M-1/61), whereas only three weaners were positive at farm C (blaCTX-M-1 group, compatible with blaCTX-M-1/61). A significant decrease in carriage was detected during the production cycle, with on average 50% carriage immediately after birth, 58% just before weaning, 29% during weaning, and 12% during finishing. The observed reduction in numbers of CTX-M-positive pigs was accompanied by a significant reduction in mean fecal counts of CTX-resistant coliforms from ∼107 CFU/g in piglets to ∼103 CFU/g in finishers (P < 0.001). These findings provide novel information about the epidemiology of ESBLs at the farm level and have important implications for assessments of risks of meat contamination during slaughter. 相似文献