(1/2363) Inhibition of vibrio anguillarum by Pseudomonas fluorescens AH2, a possible probiotic treatment of fish.

To study the possible use of probiotics in fish farming, we evaluated the in vitro and in vivo antagonism of antibacterial strain Pseudomonas fluorescens strain AH2 against the fish-pathogenic bacterium Vibrio anguillarum. As iron is important in virulence and bacterial interactions, the effect of P. fluorescens AH2 was studied under iron-rich and iron-limited conditions. Sterile-filtered culture supernatants from iron-limited P. fluorescens AH2 inhibited the growth of V. anguillarum, whereas sterile-filtered supernatants from iron-replete cultures of P. fluorescens AH2 did not. P. fluorescens AH2 inhibited the growth of V. anguillarum during coculture, independently of the iron concentration, when the initial count of the antagonist was 100 to 1, 000 times greater that of the fish pathogen. These in vitro results were successfully repeated in vivo. A probiotic effect in vivo was tested by exposing rainbow trout (Oncorynchus mykiss Walbaum) to P. fluorescens AH2 at a density of 10(5) CFU/ml for 5 days before a challenge with V. anguillarum at 10(4) to 10(5) CFU/ml for 1 h. Some fish were also exposed to P. fluorescens AH2 at 10(7) CFU/ml during the 1-h infection. The combined probiotic treatment resulted in a 46% reduction of calculated accumulated mortality; accumulated mortality was 25% after 7 days at 12 degrees C in the probiotic-treated fish, whereas mortality was 47% in fish not treated with the probiont.  (+info)

(2/2363) Dissimilatory reduction of Fe(III) and other electron acceptors by a Thermus isolate.

A thermophilic bacterium that can use O2, NO3-, Fe(III), and S0 as terminal electron acceptors for growth was isolated from groundwater sampled at a 3.2-km depth in a South African gold mine. This organism, designated SA-01, clustered most closely with members of the genus Thermus, as determined by 16S rRNA gene (rDNA) sequence analysis. The 16S rDNA sequence of SA-01 was >98% similar to that of Thermus strain NMX2 A.1, which was previously isolated by other investigators from a thermal spring in New Mexico. Strain NMX2 A.1 was also able to reduce Fe(III) and other electron acceptors. Neither SA-01 nor NMX2 A.1 grew fermentatively, i.e., addition of an external electron acceptor was required for anaerobic growth. Thermus strain SA-01 reduced soluble Fe(III) complexed with citrate or nitrilotriacetic acid (NTA); however, it could reduce only relatively small quantities (0.5 mM) of hydrous ferric oxide except when the humic acid analog 2,6-anthraquinone disulfonate was added as an electron shuttle, in which case 10 mM Fe(III) was reduced. Fe(III)-NTA was reduced quantitatively to Fe(II); reduction of Fe(III)-NTA was coupled to the oxidation of lactate and supported growth through three consecutive transfers. Suspensions of Thermus strain SA-01 cells also reduced Mn(IV), Co(III)-EDTA, Cr(VI), and U(VI). Mn(IV)-oxide was reduced in the presence of either lactate or H2. Both strains were also able to mineralize NTA to CO2 and to couple its oxidation to Fe(III) reduction and growth. The optimum temperature for growth and Fe(III) reduction by Thermus strains SA-01 and NMX2 A.1 is approximately 65 degrees C; their optimum pH is 6.5 to 7.0. This is the first report of a Thermus sp. being able to couple the oxidation of organic compounds to the reduction of Fe, Mn, or S.  (+info)

(3/2363) Vitronectin inhibits the thrombotic response to arterial injury in mice.

Vitronectin (VN) binds to plasminogen activator inhibitor-1 (PAI-1) and integrins and may play an important role in the vascular response to injury by regulating fibrinolysis and cell migration. However, the role of VN in the earliest response to vascular injury, thrombosis, is not well characterized. The purpose of this study was to test the hypothesis that variation in vitronectin expression alters the thrombotic response to arterial injury in mice. Ferric chloride (FeCl3) injury was used to induce platelet-rich thrombi in mouse carotid arteries. Wild-type (VN +/+, n = 14) and VN-deficient (VN -/-, n = 15) mice, matched for age and gender, were studied. Time to occlusion after FeCl3 injury was determined by application of a Doppler flowprobe to the carotid artery. Occlusion times of VN -/- mice were significantly shorter than those of VN +/+ mice (6.0 +/- 1.2 minutes v 17.8 +/- 2.3 minutes, respectively, P < .001). Histologic analysis of injured arterial segments showed that thrombi from VN +/+ and VN -/- mice consisted of dense platelet aggregates. In vitro studies of murine VN +/+ and VN -/- platelets showed no significant differences in ADP-induced aggregation, but a trend towards increased thrombin-induced aggregation in VN -/- platelets. Purified, denatured VN inhibited thrombin-induced platelet aggregation, whereas native VN did not. Thrombin times of plasma from VN -/- mice (20.5 +/- 2.1 seconds, n = 4) were significantly shorter than those of VN +/+ mice (34.2 +/- 6.7 seconds, n = 4, P < .01), and the addition of purified VN to VN -/- plasma prolonged the thrombin time into the normal range, suggesting that VN inhibits thrombin-fibrinogen interactions. PAI-1-deficient mice (n = 6) did not demonstrate significantly enhanced arterial thrombosis compared with wild-type mice (n = 6), excluding a potential indirect antithrombin function of VN mediated by interactions with PAI-1 as an explanation for the accelerated thrombosis observed in VN -/- mice. These results suggest that vitronectin plays a previously unappreciated antithrombotic role at sites of arterial injury and that this activity may be mediated, at least in part, by inhibiting platelet-platelet interactions and/or thrombin procoagulant activity.  (+info)

(4/2363) Down regulation by iron of prostaglandin E2 production by human synovial fibroblasts.

OBJECTIVE: To examine the effect of iron on the prostaglandin (PG) E2 production by human synovial fibroblasts in vitro. METHODS: Human synovial fibroblasts were isolated from synovial tissue of rheumatoid arthritis (RA) and osteoarthritis (OA) patients and cultured in medium. Synovial fibroblasts were stimulated by human recombinant interleukin (IL) 1 beta (0.1-10 ng/ml) with or without ferric citrate (Fe-citrate, 0.01-1 mM). The amount of PGE2 in the culture medium was measured by an enzyme linked immunosorbent assay. RESULTS: The production of PGE2 by the synovial fibroblasts was increased by stimulation with IL1 beta at all concentrations tested. Fe-citrate but not sodium citrate (Na-citrate) down regulated the production of PGE2 by the synovial fibroblasts, both with and without stimulation by IL1 beta. Fe-citrate inhibited the spontaneous PGE2 production by the cells in a dose dependent manner, and a maximum inhibition by Fe-citrate was observed at the concentration of 0.1 mM with IL1 beta stimulation. The down regulation by iron was reversed by the co-addition of desferrioxamine (100 micrograms/ml), an iron chelator. CONCLUSION: Iron down regulates the PGE2 production by synovial fibroblasts in vitro.  (+info)

(5/2363) IC202A, a new siderophore with immunosuppressive activity produced by Streptoalloteichus sp. 1454-19. I. Taxonomy, fermentation, isolation and biological activity.

IC202A, a new immunosuppressive compound, was isolated from the culture filtrate of Streptoalloteichus sp. 1454-19. It showed a suppressive effect on mixed lymphocyte culture reaction with an IC50 value of 3.6 microg/ml and mitogen induced lymphocyte blastogenesis in vitro.  (+info)

(6/2363) Amyloid beta peptides do not form peptide-derived free radicals spontaneously, but can enhance metal-catalyzed oxidation of hydroxylamines to nitroxides.

Amyloid beta (Abeta) peptides play an important role in the pathogenesis of Alzheimer's disease. Free radical generation by Abeta peptides was suggested to be a key mechanism of their neurotoxicity. Reports that neurotoxic free radicals derived from Abeta-(1-40) and Abeta-(25-35) peptides react with the spin trap N-tert-butyl-alpha-phenylnitrone (PBN) to form a PBN/.Abeta peptide radical adduct with a specific triplet ESR signal assert that the peptide itself was the source of free radicals. We now report that three Abeta peptides, Abeta-(1-40), Abeta-(25-35), and Abeta-(40-1), do not yield radical adducts with PBN from the Oklahoma Medical Research Foundation (OMRF). In contrast to OMRF PBN, incubation of Sigma PBN in phosphate buffer without Abeta peptides produced a three-line ESR spectrum. It was shown that this nitroxide is di-tert-butylnitroxide and is formed in the Sigma PBN solution as a result of transition metal-catalyzed auto-oxidation of the respective hydroxylamine present as an impurity in the Sigma PBN. Under some conditions, incubation of PBN from Sigma with Abeta-(1-40) or Abeta-(25-35) can stimulate the formation of di-tert-butylnitroxide. It was shown that Abeta peptides enhanced oxidation of cyclic hydroxylamine 1-hydroxy-4-oxo-2,2,6, 6-tetramethylpiperidine (TEMPONE-H), which was strongly inhibited by the treatment of phosphate buffer with Chelex-100. It was shown that ferric and cupric ions are effective oxidants of TEMPONE-H. The data obtained allow us to conclude that under some conditions toxic Abeta peptides Abeta-(1-40) and Abeta-(25-35) enhance metal-catalyzed oxidation of hydroxylamine derivatives, but do not spontaneously form peptide-derived free radicals.  (+info)

(7/2363) A physiological barrier distal to the anatomic blood-brain barrier in a model of transvascular delivery.

BACKGROUND AND PURPOSE: Osmotic disruption of the blood-brain barrier (BBB) provides a method for transvascular delivery of therapeutic agents to the brain. The apparent global delivery of viral-sized iron oxide particles to the rat brain after BBB opening as seen on MR images was compared with the cellular and subcellular location and distribution of the particles. METHODS: Two dextran-coated superparamagnetic monocrystalline iron oxide nanoparticle contrast agents, MION and Feridex, were administered intraarterially in rats at 10 mg Fe/kg immediately after osmotic opening of the BBB with hyperosmolar mannitol. After 2 to 24 hours, iron distribution in the brain was evaluated first with MR imaging then by histochemical analysis and electron microscopy to assess perivascular and intracellular distribution. RESULTS: After BBB opening, MR images showed enhancement throughout the disrupted hemisphere for both Feridex and MION. Feridex histochemical staining was found in capillaries of the disrupted hemisphere. Electron microscopy showed that the Feridex particles passed the capillary endothelial cells but did not cross beyond the basement membrane. In contrast, after MION delivery, iron histochemistry was detected within cell bodies in the disrupted hemisphere, and the electron-dense MION core was detected intracellularly and extracellularly in the neuropil. CONCLUSION: MR images showing homogeneous delivery to the brain at the macroscopic level did not indicate delivery at the microscopic level. These data support the presence of a physiological barrier at the basal lamina, analogous to the podocyte in the kidney, distal to the anatomic (tight junction) BBB, which may limit the distribution of some proteins and viral particles after transvascular delivery to the brain.  (+info)

(8/2363) Iron reductase for magnetite synthesis in the magnetotactic bacterium Magnetospirillum magnetotacticum.

Ferric iron reductase was purified from magnetotactic bacterium Magnetospirillum (formerly Aquaspirillum) magnetotacticum (ATCC 31632) to an electrophoretically homogeneous state. The enzyme was loosely bound on the cytoplasmic face of the cytoplasmic membrane and was found more frequently in magnetic cells than in nonmagnetic cells. The molecular mass of the purified enzyme was calculated upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis to be about 36 kDa, almost the same as that calibrated by gel filtration analysis. The enzyme required NADH and flavin mononucleotide (FMN) as optimal electron donor and cofactor, respectively, and the activity was strongly inhibited by Zn2+ acting as a partial mixed-type inhibitor. The Km values for NADH and FMN were 4.3 and 0. 035 microM, respectively, and the Ki values for Zn2+ were 19.2 and 23.9 microM for NADH and FMN, respectively. When the bacterium was grown in the presence of ZnSO4, the magnetosome number in the cells and the ferric iron reductase activity declined in parallel with an increase in the ZnSO4 concentration of the medium, suggesting that the ferric iron reductase purified in the present study may participate in magnetite synthesis.  (+info)