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排序方式: 共有1119条查询结果,搜索用时 31 毫秒
961.
Effects of pexiganan alone and combined with betalactams in experimental endotoxic shock 总被引:1,自引:0,他引:1
Giacometti A Cirioni O Ghiselli R Orlando F Kamysz W Rocchi M D'Amato G Mocchegiani F Silvestri C Łukasiak J Saba V Scalise G 《Peptides》2005,26(2):207-216
To investigate the efficacy of pexiganan, a 22-residue magainin analog, alone and combined with betalactmas antibiotics in three experimental rat models of Gram-negative septic shock. Adult male Wistar rats were given (i) an intraperitoneal injection of 1 mg Escherichia coli 0111:B4 LPS; (ii) 2x10(10)CFU of E. coli ATCC 25922; and (iii) intra-abdominal sepsis induced via cecal ligation and puncture. For each model, all animals were randomized to receive intraperitoneally isotonic sodium chloride solution, 1 mg/kg pexiganan, 1 mg/kg polymyxin B, 20 mg/kg imipenem, 60 mg/kg piperacillin alone and combined with 1 mg/kg pexiganan. Each group included 15 animals. Lethality, bacterial growth in blood or intra-abdominal fluid, endotoxin and TNF-alpha concentrations in plasma. All compounds reduced the lethality when compared to controls. Piperacillin and imipenem significantly reduced the lethality and the number of E. coli in abdominal fluid compared with saline treatment. Pexiganan showed a slightly lower antimicrobial activity than betalactams even though it achieved a substantial higher decrease in endotoxin and TNF-alpha plasma concentrations than imipenem and piperacillin. No statistically significant differences were noted for antimicrobial and antiendotoxin activities between pexiganan and polymyxin B. Combination between pexiganan and betalactams showed to be the most effective treatment in reducing all variables measured. The use of a novel antimicrobial compound able to bind to LPS associated to potent antibiotics such as betalactams may become an important future consideration for sepsis treatment. 相似文献
962.
Erica Atkins Stephanie Zamora Britny J. Candia Amy Baca Robert A. Orlando 《Cytotechnology》2005,49(1):25-37
The development of specific catalytic inhibitors for the serine protease urokinase-type plasminogen activator (uPA) has been
hindered due to difficulties in producing sufficient amounts of active recombinant uPA that is catalytically equivalent to
native uPA. The purpose of this study was to develop an efficient system for the expression of recombinant human uPA that
exhibits comparable proteolytic activity to that of the native protein. Since post-translational modifications (e.g. glycosylations)
of uPA are necessary for efficient proteolytic activity, we have used a mammalian cell line [Chinese hamster ovary (CHO)-S]
to express recombinant human uPA. CHO-S cells were selected to stably express full-length recombinant human uPA containing
a hexahistidine tag at its C-terminus to permit purification by nickel-based affinity chromatography. Secretion of recombinant
uPA into the culture media was confirmed by immunoblotting and the presence of an N-linked glycosylation was confirmed by PNGase sensitivity. Enzymatic activity of purified recombinant uPA was demonstrated
using zymography and quantitatively compared to native uPA by kinetic analysis using an uPA-specific substrate. Native uPA
and the recombinant uPA demonstrated comparable Km values (55.7 and 39 μM, respectively). Furthermore, inhibition studies using benzamidine resulted in a Ki of 195 μM for native uPA, while recombinant uPA had a Ki of 112 μM. These data indicate that recombinant human uPA expressed by CHO-S cells is functionally comparable to native uPA. 相似文献
963.
Mayorga LS 《BioEssays : news and reviews in molecular, cellular and developmental biology》2005,27(2):232; author reply 232-232; author reply 233
964.
965.
Site-specific incorporation of N-(deoxyguanosin-8-yl)-2-acetylaminofluorene (dG-AAF) into oligonucleotides using modified 'ultra-mild' DNA synthesis
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Aromatic amino and nitro compounds are potent carcinogens found in the environment that exert their toxic effects by reacting with DNA following metabolic activation. One important adduct is N-(deoxyguanosin-8-yl)-2-acetylaminofluorene (dG-AAF), which has been extensively used in studies of the mechanisms of DNA repair and mutagenesis. Despite the importance of dG-AAF adducts in DNA, an efficient method for its incorporation into DNA using solid-phase synthesis is still missing. We report the development of a modified ‘ultra-mild’ DNA synthesis protocol that allows the incorporation of dG-AAF into oligonucleotides of any length accessible by solid-phase DNA synthesis with high efficiency and independent of sequence context. Key to this endeavor was the development of improved deprotection conditions (10% diisopropylamine in methanol supplemented with 0.25 M of β-mercaptoethanol) designed to remove protecting groups of commercially available ‘ultra-mild’ phosphoramidite building blocks without compromising the integrity of the exquisitely base-labile acetyl group at N8 of dG-AAF. We demonstrate the suitability of these oligonucleotides in the nucleotide excision repair reaction. Our synthetic approach should facilitate comprehensive studies of the mechanisms of repair and mutagenesis induced by dG-AAF adducts in DNA and should be of general use for the incorporation of base-labile functionalities into DNA. 相似文献
966.
Wilson AE Sarnelle O Neilan BA Salmon TP Gehringer MM Hay ME 《Applied and environmental microbiology》2005,71(10):6126-6133
To measure genetic variation within and among populations of the bloom-forming cyanobacterium Microcystis aeruginosa, we surveyed a suite of lakes in the southern peninsula of Michigan that vary in productivity (total phosphorus concentrations of approximately 10 to 100 microg liter(-1)). Survival of M. aeruginosa isolates from lakes was relatively low (i.e., mean of 7% and maximum of 30%) and positively related to lake total phosphorus concentration (P = 0.014, r2 = 0.407, n = 14). In another study (D. F. Raikow, O. Sarnelle, A. E. Wilson, and S. K. Hamilton, Limnol. Oceanogr. 49:482-487, 2004), survival rates of M. aeruginosa isolates collected from an oligotrophic lake (total phosphorus of approximately 10 mug liter(-1) and dissolved inorganic nitrogen:total phosphorus ratio of 12.75) differed among five different medium types (G test, P of <0.001), with higher survival (P = 0.003) in low-nutrient media (28 to 37% survival) than in high-nutrient media. Even with the relatively low isolate survivorship that could select against detecting the full range of genetic variation, populations of M. aeruginosa were genetically diverse within and among lakes (by analysis of molecular variance, Phi(sc) = 0.412 [Phi(sc) is an F-statistic derivative which evaluates the correlation of haplotypic diversity within populations relative to the haplotypic diversity among all sampled populations], P = 0.001), with most clones being distantly related to clones collected from lakes directly attached to Lake Michigan (a Laurentian Great Lake) and culture collection strains collected from Canada, Scotland, and South Africa. Ninety-one percent of the 53 genetically unique M. aeruginosa clones contained the microcystin toxin gene (mcyA). Genotypes with the toxin gene were found in all lakes, while four lakes harbored both genotypes possessing and genotypes lacking the toxin gene. 相似文献
967.
968.
Sarnelle O 《The American naturalist》2003,161(3):478-496
The assumption that per capita consumer effects on prey density are independent of consumer and prey density is examined with a large-scale manipulation of an aquatic herbivore (Daphnia). A gradient of consumer removal was maintained long enough to allow the abundances of both consumer and prey (phytoplankton) to equilibrate to the manipulation. Strong and unequivocal nonlinearities were found in the effect of Daphnia on total phytoplankton abundance and the abundance of most of the common phytoplankton species. Daphnia's suppression of phytoplankton was strong between 0 and approximately 400 microg Daphnia L(-1) but essentially nil from approximately 400 to 900 microg Daphnia L(-1). The sharp deceleration in Daphnia's effect was not caused by a shift within the phytoplankton community toward consumption-resistant forms. The most likely explanation for the deceleration was a reduction in Daphnia's filtering effort at low phytoplankton abundance, that is, a Type III functional response. A review of experimental literature suggested that decelerating effects of consumers are the norm in aquatic systems. Nonlinear effects present problems for the estimation of interaction strength and the building of community interaction models from the results of predator manipulations. It is suggested that the role of field experiments in community ecology should be to test rather than to parameterize models. 相似文献
969.
Torres-Fernández O Ordóñez N 《Biomédica : revista del Instituto Nacional de Salud》2003,23(2):225-231
The fungal cell wall viewed through the electron microscope appears transparent when fixed by the conventional osmium tetroxide method. However, ruthenium tetroxide post-fixing has revealed new details in the ultrastructure of Penicillium sp. hyphae and Saccharomyces cerevisiae yeast. Most significant was the demonstration of two or three opaque diverse electron dense layers on the cell wall of each species. Two additional features were detected. Penicillium septa presented a three-layered appearance and budding S. cerevisiae yeast cell walls showed inner filiform cell wall protrusions into the cytoplasm. The combined use of osmium tetroxide and ruthenium tetroxide is recommended for post-fixing in electron microscopy studies of fungi. 相似文献
970.