Search results for "Bacterial"
showing 10 items of 3246 documents
Toxicity and mode of action of Bacillus thuringiensis Cry proteins in the Mediterranean corn borer, Sesamia nonagrioides (Lefebvre)
2006
ABSTRACT Sesamia nonagrioides is one of the most damaging pests of corn in Spain and other Mediterranean countries. Bt corn expressing the Bacillus thuringiensis Cry1Ab toxin is being grown on about 58,000 ha in Spain. Here we studied the mode of action of this Cry protein on S. nonagrioides (binding to specific receptors, stability of binding, and pore formation) and the modes of action of other Cry proteins that were found to be active in this work (Cry1Ac, Cry1Ca, and Cry1Fa). Binding assays were performed with 125 I- or biotin-labeled toxins and larval brush border membrane vesicles (BBMV). Competition experiments indicated that these toxins bind specifically and that Cry1Aa, Cry1Ab, an…
Superoxide generation by human neutrophils induced by low doses of Escherichia coli hemolysin.
1991
Escherichia coli hemolysin (Hly) was isolated from bacterial culture supernatants by polyethylene glycol precipitation and centrifugation in glycerol density gradients. The toxin preparations contained less than 1 mol of lipopolysaccharide per 10 mol of protein, and they had no fatty acids. The capacity of purified hemolysin to stimulate superoxide anion production in polymorphonuclear leukocytes was monitored kinetically in a lumimeter by using the lucigenin assay and was correlated with the kinetics of transmembrane pore formation. When applied to leukocytes suspended in protein-free buffer, very low concentrations (0.02 to 0.1 HU/ml) of the toxin strongly stimulated the production of sup…
Assembly mechanism of the oligomeric streptolysin O pore: the early membrane lesion is lined by a free edge of the lipid membrane and is extended gra…
1998
Streptolysin O (SLO) is a bacterial exotoxin that binds to cell membranes containing cholesterol and then oligomerizes to form large pores. Along with rings, arc-shaped oligomers form on membranes. It has been suggested that each arc represents an incompletely assembled oligomer and constitutes a functional pore, faced on the opposite side by a free edge of the lipid membrane. We sought functional evidence in support of this idea by using an oligomerization-deficient, non-lytic mutant of SLO. This protein, which was created by chemical modification of a single mutant cysteine (T250C) with N-(iodoacetaminoethyl)-1-naphthylamine-5-sulfonic acid, formed hybrid oligomers with active SLO on memb…
Differential interaction of the two cholesterol-dependent, membrane-damaging toxins, streptolysin O and Vibrio cholerae cytolysin, with enantiomeric …
2003
AbstractMembrane cholesterol is essential to the activity of at least two structurally unrelated families of bacterial pore-forming toxins, represented by streptolysin O (SLO) and Vibrio cholerae cytolysin (VCC), respectively. Here, we report that SLO and VCC differ sharply in their interaction with liposome membranes containing enantiomeric cholesterol (ent-cholesterol). VCC had very low activity with ent-cholesterol, which is in line with a stereospecific mode of interaction of this toxin with cholesterol. In contrast, SLO was only slightly less active with ent-cholesterol than with cholesterol, suggesting a rather limited degree of structural specificity in the toxin–cholesterol interact…
Soluble N-ethylmaleimide-sensitive-factor attachment protein and N-ethylmaleimide-insensitive factors are required for Ca2+-stimulated exocytosis of …
1996
Ca2+ stimulates exocytosis in permeabilized insulin-secreting cells. To investigate the putative cytosolic components involved in the Ca2+ response, HIT-T15 cells (a pancreatic B-cell line) were permeabilized with streptolysin-O, a procedure that allows rapid exchange of soluble components including macromolecules. We found that in this cell preparation the secretory response to Ca2+ but not to guanosine 5'-[gamma-thio]triphosphate was lost as a function of time and could be restored by rat brain cytosol in a concentration-dependent manner. Reconstitutive activity of rat brain cytosol was found in a high-molecular-mass heat-labile partially N-ethylmaleimide(NEM)-sensitive fraction. The NEM-…
Essential oils of Salvia bracteata and Salvia rubifolia from Lebanon: Chemical composition, antimicrobial activity and inhibitory effect on human mel…
2009
Aim of the study: Salvia bracteata Banks et Sol. and Salvia rubifolia Boiss. are known in folk medicine of Lebanon for the treatment of microbial infections, cancer, urinary and pulmonary problems. In the present study the chemical composition and antimicrobial activity of essential oils from aerial parts of Salvia bracteata and Salvia rubifolia collected in Lebanon were evaluated. The oils were also tested for their potential antiproliferative effects against M14 human melanoma cells. Material and methods: The oils were studied by GC and GC-MS and their antibacterial activity (MIC and MBC) was tested against ten bacteria species using the broth dilution method. The inhibitory effect on hum…
Induction of programmed cell death in human retinoblastoma Y79 cells by C2-ceramide.
1998
C2-ceramide, a cell-permeable analogue of ceramide, induced significant, dose- and time-dependent death in human retinoblastoma Y79 cells. Dying cells strongly displayed the morphology of apoptosis as characterized by microscopic evidence of cell shrinkage, membrane blebbing, nuclear and chromatin condensation and degeneration of the nucleus into membrane-bound apoptotic bodies. Upon induction of apoptosis Y79 cells evidence early phosphatidylserine externalization, as shown by annexin V-FITC. Apoptosis was also assessed by monitoring changes in cell granularity by staining with the combined fluorescent dyes acridine orange and ethidium bromide. C2-ceramide induced these morphological chang…
Dissolution enhancement and in vitro performance of clarithromycin nanocrystals produced by precipitation–lyophilization–homogenization method
2014
The gastroduodenal diseases caused by Helicobacter pylori were commonly treated with antibiotic clarithromycin as a standard regimen. According to the poorly water-soluble of clarithromycin, the nanocrystal formulation was prepared. The aim of this study was to investigate an enhancement effect of clarithromycin nanocrystals produced by precipitation-lyophilization-homogenization (PLH) method on the saturation solubility, dissolution velocity, antibiotic activity, permeability through the gastric mucus and cellular permeability. Poloxamer 407 and sodium lauryl sulfate (SLS) were chosen as combined stabilizers in the nanocrystal system. The obtained clarithromycin nanocrystals were identifie…
From anti-fouling to biofilm inhibition: New cytotoxic secondary metabolites from two Indonesian Agelas sponges
2010
Chemical investigation of Indonesian marine sponges Agelas linnaei and A. nakamurai afforded 24 alkaloid derivatives representing either bromopyrrole or diterpene alkaloids. A. linnaei yielded 16 bromopyrrole alkaloids including 11 new natural products with the latter exhibiting unusual functionalities. The new compounds include the first iodinated tyramine-unit bearing pyrrole alkaloids, agelanesins A-D. These compounds exhibited cytotoxic activity against L5178Y mouse lymphoma cells with IC(50) values between 9.25 and 16.76 muM. Further new compounds include taurine acid substituted bromopyrrole alkaloids and a new dibromophakellin derivative. A. nakamurai yielded eight alkaloids among th…
An organogold compound as potential antimicrobial agent against drug resistant bacteria: Initial mechanistic insights
2021
Abstract The rise of antimicrobial resistance has necessitated novel strategies to efficiently combat pathogenic bacteria. Metal‐based compounds have been proven as a possible alternative to classical organic drugs. Here, we have assessed the antibacterial activity of seven gold complexes of different families. One compound, a cyclometalated Au(III) C^N complex, showed activity against Gram‐positive bacteria, including multi‐drug resistant clinical strains. The mechanism of action of this compound was studied in Bacillus subtilis. Overall, the studies point towards a complex mode of antibacterial action, which does not include induction of oxidative stress or cell membrane damage. A number …