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排序方式: 共有191条查询结果,搜索用时 234 毫秒
121.
122.
Stefan Nehring 《Helgoland Marine Research》2006,60(2):127-134
In one of the largest European rivers, the Elbe, from its source in the Czech Republic to the German North Sea, 31 alien macrozoobenthic species have been recorded in total. Most of these species have been introduced by shipping activities. With a total number of 21 species, many of the established aliens occur—partly exclusively—in the brackish area of the Elbe estuary. In order to explain this observed settlement characteristic, four main arguments come into consideration: (1) estuaries with intensive international shipping have a higher potential infection rate than other aquatic zones; (2) brackish water species have, due to specific physiological characteristics, a better chance of being transported alive than euhaline or freshwater species and they also probably have a higher perennation and establishment potential after release; (3) brackish waters have the greatest natural ‘indigenous species minimum’, so that more alien species can potentially establish; and (4) salt-tolerant limnetic alien species introduced into inland water reached the coast at first in the estuaries. It seems that the combination of brackish water with its unsaturated ecological niches and intensive international ship traffic has the highest potential infection rate for aquatic systems with alien macrozoobenthic species. And, estuaries are subjected to a two-sided invasion pressure by alien species, via the ocean (mainly shipping) and via inland waters (mainly shipping canal construction). The identification of such patterns is an important prerequisite for the development of a forward-looking alien monitoring and management strategy. 相似文献
123.
Kathryn E Wheatley Corey JA Bradshaw Robert G Harcourt Lloyd S Davis Mark A Hindell 《BMC veterinary research》2006,2(1):1-8
Background
Postweaning diarrhoea (PWD) in pigs is usually the main infectious problem of large-scale farms and is responsible for significant losses worldwide. The disease is caused mainly by enterotoxigenic E. coli (ETEC) and Shiga-toxin producing E. coli (STEC). In this study a total of 101 E. coli isolated from pigs with PWD in Slovakia were characterized using phenotypic and genotypic methods.Results
These 101 isolates belonged to 40 O:H serotypes. However, 57% of the isolates belonged to only six serotypes (O9:H51, O147:H-, O149:H10, O163:H-, ONT:H-, and ONT:H4), including two new serotypes (O163:H- and ONT:H4) not previously found among porcine ETEC and STEC isolated in other countries. Genes for EAST1, STb, STa, LT and Stx2e toxins were identified in 64%, 46%, 26%, 20%, and 5% of isolates, respectively. PCR showed that 35% of isolates carried genes for F18 colonization factor, and further analyzed by restriction endonuclease revealed that all of them were F18ac. Genes for F4 (K88), F6 (P987), F17, F5 (K99), F41, and intimin (eae gene) adhesins were detected in 19 %, 5%, 3%, 0.9%, 0.9%, and 0.9% of the isolates, respectively. The study of genetic diversity, carried out by PFGE of 46 representative ETEC and STEC isolates, revealed 36 distinct restriction profiles clustered in eight groups. Isolates of the same serotype were placed together in the dendrogram, but high degree of polymorphism among certain serotypes was detected.Conclusion
Seropathotype O149:H10 LT/STb/EAST1/F4 (14 isolates) was the most commonly detected followed by O163:H- EAST1/F18 (six isolates), and ONT:H4 STa/STb/Stx2e/F18 (five isolates). Interestingly, this study shows that two new serotypes (O163:H- and ONT:H4) have emerged as pig pathogens in Slovakia. Furthermore, our results show that there is a high genetic variation mainly among ETEC of O149:H10 serotype. 相似文献124.
Price DJ Campbell PG Sutton AG Grech ED Davies A Hall JA De Belder MA 《International journal of cardiovascular interventions》2001,4(1):15-20
BACKGROUND: The EPISTENT trial reported improved early outcomes with routine use of abciximab after coronary stenting. Increasing use of stents means that routine abciximab adds significantly to costs of percutaneous coronary intervention (PCI). This paper reports the results of a protocol encouraging restriction of abciximab therapy to high-risk patients only. METHODS: Data were collected prospectively over a 34-month period for patients undergoing PCI with stenting. In addition to those who fulfilled criteria for inclusion in the EPISTENT trial, patients treated in the setting of acute myocardial infarction (AMI) were studied. Demographic data, procedural details and early clinical outcomes were recorded. RESULTS: Of 808 patients studied, 601 fulfilled EPISTENT inclusion criteria and comprised 367 patients (45%) treated for stable angina and 234 (30%) treated for unstable or post-infarct angina. The additional 207 patients (25%) were treated during AMI. The 808 patients received a total of 981 stents. Abciximab was given in only 88 cases (10.9%). Major adverse clinical events occurred in 39 patients (4.8%). CONCLUSION: Selective use of abciximab for patients undergoing coronary stenting can be associated with outcomes equivalent to those reported for routine use, but with significant cost savings. 相似文献
125.
Proteinase-activated receptor-1 regulation of macrophage elastase (MMP-12) secretion by serine proteinases 总被引:7,自引:0,他引:7
Raza SL Nehring LC Shapiro SD Cornelius LA 《The Journal of biological chemistry》2000,275(52):41243-41250
The serine proteinases plasmin and thrombin convert proenzyme matrix metalloproteinases (MMPs) into catalytically active forms. In addition, we demonstrate that plasmin(ogen) and thrombin induce a significant increase in secretion of activated murine macrophage elastase (MMP-12) protein. Active serine protease is responsible for induction, as demonstrated by the absence of MMP-12 induction in plasminogen(Plg)-treated urokinase-type plasminogen activator-deficient macrophages. Since increased MMP-12 protein secretion was not accompanied by an increase in MMP-12 mRNA, we examined post-translational mechanisms. Protein synthesis was not required for early release of MMP-12 but was required for later secretion of activated enzyme. Immunofluorescent microscopy demonstrated basal expression in macrophages that increased following serine proteinase exposure. Inhibition of MMP-12 secretion by hirudin and pertussis toxin demonstrated a role for the thrombin G protein-coupled receptor (protease-activated receptor 1 (PAR-1)). PAR-1-activating peptides were able to induce MMP-12 release. Investigation of signal transduction pathways involved in this response demonstrate the requirement for protein kinase C, but not tyrosine kinase, activity. These data demonstrate that plasmin and thrombin regulate MMP-12 activity through distinct mechanisms: post-translational secretion of preformed MMP-12 protein, induction of protein secretion that is protein kinase C-mediated, and extracellular enzyme activation. Most importantly, we show that serine proteinase MMP-12 regulation in macrophages occurs via the protein kinase C-activating G protein-coupled receptor PAR-1. 相似文献
126.
127.
128.
A rate-independent technique for analysis of nucleic acid sequences: evolutionary parsimony 总被引:24,自引:1,他引:23
The method of evolutionary parsimony--or operator invariants--is a
technique of nucleic acid sequence analysis related to parsimony analysis
and explicitly designed for determining evolutionary relationships among
four distantly related taxa. The method is independent of substitution
rates because it is derived from consideration of the group properties of
substitution operators rather than from an analysis of the probabilities of
substitution in branches of a tree. In both parsimony and evolutionary
parsimony, three patterns of nucleotide substitution are associated
one-to-one with the three topologically linked trees for four taxa. In
evolutionary parsimony, the three quantities are operator invariants. These
invariants are the remnants of substitutions that have occurred in the
interior branch of the tree and are analogous to the substitutions assigned
to the central branch by parsimony. The two invariants associated with the
incorrect trees must equal zero (statistically), whereas only the correct
tree can have a nonzero invariant. The chi 2-test is used to ascertain the
nonzero invariant and the statistically favored tree. Examples, obtained
using data calculated with evolutionary rates and branchings designed to
camouflage the true tree, show that the method accurately predicts the
tree, even when substitution rates differ greatly in neighboring peripheral
branches (conditions under which parsimony will consistently fail). As the
number of substitutions in peripheral branches becomes fewer, the parsimony
and the evolutionary-parsimony solutions converge. The method is robust and
easy to use.
相似文献
129.
Ralf B. Nehring Franklin Gu Hsin-Yu Lin Janet L. Gibson Martin J. Blythe Ray Wilson María Angélica Bravo?Nú?ez P. J. Hastings Edward J. Louis Ryan L. Frisch James C. Hu Susan M. Rosenberg 《Nucleic acids research》2016,44(5):e41
With the wide availability of whole-genome sequencing (WGS), genetic mapping has become the rate-limiting step, inhibiting unbiased forward genetics in even the most tractable model organisms. We introduce a rapid deconvolution resource and method for untagged causative mutations after mutagenesis, screens, and WGS in Escherichia coli. We created Deconvoluter—ordered libraries with selectable insertions every 50 kb in the E. coli genome. The Deconvoluter method uses these for replacement of untagged mutations in the genome using a phage-P1-based gene-replacement strategy. We validate the Deconvoluter resource by deconvolution of 17 of 17 phenotype-altering mutations from a screen of N-ethyl-N-nitrosourea-induced mutants. The Deconvoluter resource permits rapid unbiased screens and gene/function identification and will enable exploration of functions of essential genes and undiscovered genes/sites/alleles not represented in existing deletion collections. This resource for unbiased forward-genetic screens with mapping-by-sequencing (‘forward genomics’) demonstrates a strategy that could similarly enable rapid screens in many other microbes. 相似文献
130.
Alves-Gomes JA; Orti G; Haygood M; Heiligenberg W; Meyer A 《Molecular biology and evolution》1995,12(2):298-318
The order Gymnotiformes (South American electric fishes) is a fascinating
assemblage of freshwater fishes that share the unusual ability to produce
and sense electric fields used for electrolocation and social
communication. In the last few decades, the electrogenic and electrosensory
systems (EES) of these fish have served as an excellent model to study
motor and sensory physiology in vertebrates. In an attempt to the evolution
of characters associated with the EES in the group, we applied
maximum-parsimony (MP), minimum-evolution (ME), and maximum-likelihood (ML)
methods to analyze 302 aligned bases of the mitochondrial 12S rRNA and 416
bases of the mitochondrial 16S rRNA of 19 gymnotiform genera representing
all six recognized families. Six catfish genera (order Siluriformes) were
also sequenced and used as outgroups. The phylogenetic hypothesis resultant
from molecular data analysis differs in some respects from previous
hypotheses based on morphological studies. Our results were most
informative within the family level, as we were unable to elucidate the
relationships among deeper branches in this order with sufficient
confidence by using molecular data alone. The phylogenetic information of
both mitochondrial DNA segments appears to be affected by functional
constraints, and the resultant topologies were sensitive to different
weighting schemes and the algorithm used. Nonetheless, we found unanimous
support for the following phylogenetic relationships: (1) the family
Sternopygidae is an unnatural group, and Sternopygus is the sole
representative of a unique lineage within the order; (2) the family
Hypopomidae is not monophyletic; and (3) the order Gymnotiformes is
composed of at least six natural clades: Sternopygus, family Apteronotidae,
a new clade consisting of the remaining sternopygids, families Hypopomidae
+ Rhamphicthyidae, family Electrophoridae, and family Gymnotidae. By
combining molecular, morphological, and physiological information, we
propose a new hypothesis for the phylogeny of this group and suggest a new
family Eigenmanniidae n. (order Gymnotiformes).
相似文献