Effects of the cationic antimicrobial peptide eumenitin from the venom of solitary wasp Eumenes rubronotatus in planar lipid bilayers: Surface charge and pore formation activity

Eumenitin, a novel cationic antimicrobial peptide from the venom of solitary wasp Eumenes rubronotatus, was characterized by its effects on black lipid membranes of negatively charged (azolectin) and zwitterionic (1,2-diphytanoyl-sn-glycero-3-phosphocholine (DPhPC) or DPhPC-cholesterol) phospholipids: surface potential changes, single-channel activity, ion selectivity, and pore size were studied. We found that eumenitin binds preferentially to charged lipid membranes as compared with zwitterionic ones. Eumenitin is able to form pores in azolectin (G(1) = 118.00 +/- 3.67 pS or G(2) = 160.00 +/- 7.07 pS) and DPhPC membranes (G = 61.13 +/- 7.57 pS). Moreover, cholesterol addition to zwitterionic DPhPC membranes inhibits pore formation activity but does not interfere with the binding of peptide. Open pores presented higher cation (K (+)) over anion (Cl-) selectivity. The pore diameter was estimated at between 8.5and 9.8 angstrom in azolectin membranes and about 4.3 angstrom in DPhPC membranes. The results are discussed based on the toroidal pore model for membrane pore-forming activity and ion selectivity. (c) 2007 Elsevier Ltd. All rights reserved.

The Antiapoptotic Effect of Granulocyte Colony-stimulating Factor Reduces Infarct Size and Prevents Heart Failure Development in Rats

Background/Aim. Granulocyte colony-stimulating factor (G-CSF) reduces myocardial injury and improves cardiac function after myocardial infarction (MI). We investigated the early alterations provided by G-CSF and the chronic repercussions in infarcted rats. Methods. Male Wistar rats (200-250g) received vehicle (MI) or G-CSF (MI-GCSF) (50 mu g/kg, sc) at 7, 3 and 1 days before MI surgery. Afterwards MI was produced and infarct size was measured 1 and 15 days after surgery. Expression of anti-and proapoptotic proteins was evaluated immediately before surgery. 24 hours after surgery, apoptotic nuclei were evaluated. Two weeks after MI, left ventricular (LV) function was evaluated, followed by in situ LV diastolic pressure-volume evaluation. Results. Infarct size was decreased by 1 day pretreatment before occlusion (36 +/- 2.8 vs. 44 +/- 2.1% in MI; P<0.05) and remained reduced at 15 days after infarction (28 +/- 2.2 vs. 36 +/- 1.4% in MI; P<0.05). G-CSF pretreatment increased Bcl-2 and Bcl-xL protein expression, but did not alter Bax in LV. Apoptotic nuclei were reduced by treatment (Sham: 0.46 +/- 0.42, MI: 15.5 +/- 2.43, MI-GCSF: 5.34 +/- 3.34%; P<0.05). Fifteen days after MI, cardiac function remained preserved in G-CSF pretreated rats. The LV dilation was reduced in MI-G-CSF group as compared to MI rats, being closely associated with infarct size. Conclusion. The early beneficial effects of G-CSF were essentials to preserve cardiac function at a chronic stage of myocardial infarction. Copyright (C) 2011 S. Karger AG, Basel

The effect of DMSA-functionalized magnetic nanoparticles on transendothelial migration of monocytes in the murine lung via a beta(2) integrin-dependent pathway

Magnetic nanoparticles surface-functionalized with meso-2,3-dimercaptosuccinic acid (MNPs-DMSA) constitute an innovative and promising approach for tissue- and cell-targeted delivery of therapeutic drugs in the lung. Transendothelial migration of leukocytes in the lung is a side effect of endovenous administration of MNPs-DMSA. Using cytologic and phenotypic analysis of murine bronchoalveolar lavage cells, we identified monocytes/macrophages as the main subpopulation of leukocytes involved in this process. Moreover, ultrastructural analysis revealed the presence of nanoparticles inside of numerous macrophages from bronchoalveolar lavage. MNPs-DMSA at concentrations as high as 1 X 10(15) nanoparticles/mL had no toxic effects on macrophages, as evidenced by 3-(4, 5-dimethylthiazolyi-2)-2,5-diphenyltetrazolium bromide (MTT) assay. Notably, MNPs-DMSA up-regulated the mRNA expression of E, L- and P-selectin and macrophage-1 antigen in the murine lung. Upregulation of these cell adhesion molecules was associated with an increased concentration of tumor necrosis factor-alpha in lung. Finally, the critical relevance of the beta(2) integrin-dependent pathway in leukocyte transmigration elicited by MNPs-DMSA was demonstrated by use of knockout mice. Our results characterize mechanisms of the pro-inflammatory effects of MNPs-DMSA in the lung, and identify beta(2) integrin-targeted interventions as promising strategies to reduce pulmonary side effects of MNPs-DMSA during biomedical applications. (C) 2009 Elsevier Ltd. All rights reserved.

Relative contribution of pre- and post-synaptic effects to the neostigmine-induced recovery of neuromuscular transmission blocked by vecuronium

The relative contribution of the pre- and post-synaptic effects to the neostigmine-induced recovery of neuromuscular transmission blocked by vecuronium was studied. A conjunction of myographical and electrophysiological techniques was employed. The preparation was the sciatic nerve-extensor digitorum longus muscle of the rat, in vitro. The physiological variables recorded were nerve-evoked twitches (generated at 0.1 Hz), tetanic contractions (generated at 50 Hz) and end-plate potentials (epps), generated in trains of 50 Hz. The epps were analyzed in: amplitude of first epp in the train; mean amplitude of the 30th to the 59th epp in the train (epps-plateau); half-decay time of the epp; early tetanic rundown of epps in the train; plateau tetanic rundown of epps in the train; quantal content of the epps and quantal size. In myographical experiments, a concentration of vecuronium was found (0.8 mu m) that affected both twitches and tetanic contractions and a concentration of neostigmine was found (0.048 mu m) that completely restored the twitch affected by vecuronium. The cellular effects of vecuronium and neostigmine, studied alone or in association, in the above-mentioned concentrations, were scrutinized by means of electrophysiological techniques. These showed that vecuronium alone decreased the peak amplitude, the quantal content of epps and the quantal size and reinforced the tetanic rundown of epps. Neostigmine alone increased the peak amplitude, the quantal content and the half-decay time of the epps. When employed in the presence of vecuronium, neostigmine increased both the quantal content of the epps (via a presynaptic effect) and the half-decay time of the epps (via a postsynaptic effect). Seeing the pre- and the post-synaptic effects of neostigmine were of similar magnitude, they permit to conclude that both these effects contributed significantly to the restoration by neostigmine of the neuromuscular transmission blocked by vecuronium.

BnP1, a novel P-I metalloproteinase from Bothrops neuwiedi venom: Biological effects benchmarking relatively to jararhagin, a P-IIISVMP

Snake venom metalloproteinases (SVMPs) have been extensively studied and their effects associated with the local bleeding observed in human accidents by viper snakes. Representatives of P-I and P-III classes of SVMPs similarly hydrolyze extracellular matrix proteins or coagulation factors while only P-III SVMPs induce significant hemorrhage in experimental models. In this work, the effects of P-I and P-III SVMPs on plasma proteins and cultures of muscle and endothelial cells were compared in order to enlighten the mechanisms involved in venom-induced hemorrhage. To reach this comparison, BnP1 was isolated from B. neuwiedi venom and used as a weakly hemorrhagic P-I SVMPs and jararhagin was used as a model of potently hemorrhagic P-III SVMP. BnP1 was isolated by size exclusion and anion-exchange chromatographies, showing apparent molecular mass of approximately 24kDa and sequence similarity with other members of SVMPs, which allowed its classification as a group P-I SVMP. The comparison of local effects induced by SVMPs showed that BnP1 was devoid of significant myotoxic and hemorrhagic activities and jararhagin presented only hemorrhagic activity. BnP1 and jararhagin were able to hydrolyze fibrinogen and fibrin, although the latter displayed higher activity in both systems. Using HUVEC primary cultures, we observed that BnP1 induced cell detachment and a decrease in the number of viable endothelial cells in levels comparable to those observed by treatment with jararhagin. Moreover, both BnP1 and jararhagin induced apoptosis in HUVECs while only a small increase in LDH supernatant levels was observed after treatment with jararhagin, suggesting that the major mechanism involved in endothelial cell death is apoptosis. Jararhagin and BnP1 induced little effects on C2C12 muscle cell cultures, characterized by a partial detachment 24h after treatment and a mild necrotic effect as evidenced by a small increase in the supernatants LDH levels. Taken together, our data show that P-I and P-III SVMPs presented comparable effects except for the hemorrhagic activity, suggesting that hydrolysis of coagulation factors or damage to endothelial cells are not sufficient for induction of local bleeding. (C) 2007 Elsevier Ltd. All rights reserved.

Effects of Synthesis Conditions on the Nanostructure of Hybrid Sols Produced by the Hydrolytic Condensation of (3-Methacryloxypropyl)trimethoxysilane

Polysilsesquioxanes containing methacrylate pendant groups were prepared by the sol-gel process through hydrolysis and condensation of (3-methacryloxypropyl)trimethoxysilane (MPTS) dissolved in a methanol/methyl methacrylate (MMA) mixture. The effects of different water, MMA, and methanol contents, as well as of pH, on the nanoscopic and local structures of the system, at advanced stages of the condensation reaction, were studied by small-angle X-ray scattering (SAXS) and (29)Si nuclear magnetic resonance (NMR) spectroscopy, respectively. SAXS results indicate that the nanoscopic features of the hybrid sol could be described by a hierarchical model composed of two levels, namely (i) silsesquioxane (SSQO) nanoparticles Surrounded by the methacrylate pendant groups and the methanol/MMA mixture. and (ii) aggregation zones or islands containing correlated SSQO nanoparticles, embedded in the liquid medium. The (29)Si NMR results Show that the inner Structures of SSQO nanoparticles produced at pH 1 and 3 were built Up of polyhedral structures. mainly cagelike octamers and small linear oligomers, respectively. Irrespective of MMA and methanol contents, for a [H(2)O]/[MPTS] ratio higher than or equal to 1, the SSQO nailoparticles produced at pH I exhibit an average condensation degree (CD approximate to 69-87%) and average radius of gyration (R(g) approximate to 2.5 angstrom) larger than those produced at pH 3 (CD approximate to 48-67% and R(g) approximate to 1.5 angstrom). Methanol appears to act as a redispersion agent, by decreasing the number of particles inside the aggregation zones, while the addition of MMA induces a swelling of the aggregation zones.

Magnetic characterization of ferrihydrite nanoparticles synthesized by hydrolysis of Fe metal-organic precursor

We investigate the formation of ferrihydrite nanoparticles (NPs) by hydrolysis of the Fe(III) alkoxide Fe(O(t)Bu)(3). Controlled amounts of water, up to 3.0 vol%, were added to the precursor solution yielding a series of hydrolyzed samples ranging from P0.0 (the unreacted precursor) to P3.0. X-ray diffraction (XRD) analysis evidenced the formation of high-crystalline ferrihydrite NP in sample P3.0, with grain size estimate of about 3.2 nm. The transition from the molecular precursor to the formation of crystalline magnetic NPs was followed through magnetization measurements M(T) and M(H), as well as Mossbauer spectroscopy (MS). M(T) measurements indicate a paramagnetic (PM) behavior for sample P0.0, characteristic of binuclear Fe-O-Fe units, which evolves to a superparamagnetic (SPM) behavior, with an energy barrier for the blocking process estimated for sample P3.0 as E(a) = 4.9 x 10(-21) J (E(a)/k(B) = 355 K), resulting in a high effective anisotropy constant K(eff) = 290 kJ/m(3). Magnetization loops at 5 K progressively change from PM-like to ferromagnetic-like shape upon increasing the hydrolysis process, although hysteresis (H(c) approximate to 500 Oe) only is apparent for P2.0 and higher. MS spectra at room temperature are PM/SPM doublets for all samples, while the MS spectra at T = 4.2 K reveal increasingly well-defined magnetic ordering as hydrolysis of the precursor stepwise progresses until well-crystallized ferrihydrite particles are formed. (C) 2008 Elsevier B.V. All rights reserved.

Ion dependence of magnetic anisotropy in MFe(2)O(4) (M = Fe, Co, Mn) nanoparticles synthesized by high-temperature reaction

The influence of different M(2+) cations on the effective magnetic anisotropy of systems composed of MFe(2)O(4) (M Fe, Co and Mn) nanoparticles was investigated. Samples were prepared by the high-temperature (538 K) solution phase reaction of Fe (acac) 3, Co (acac) 2 and Mn (acac) 2 with 1,2 octanodiol in the presence of oleic acid and oleylamine. The final particles are coated by an organic layer of oleic acid that prevents agglomeration. Transmission electron microscopy (TEM) images show that particles present near spherical form and a narrow grain size distribution, with mean diameters in the range of 4.5 - 7.6 nm. Powder samples were analyzed by ac susceptibility and Mossbauer measurements, and K(eff) for all samples was evaluated using both techniques, showing a strong dependence on the nature of the divalent cation. (C) 2008 Elsevier B.V. All rights reserved.

Magnetic and structural properties of NiFe(2)O(4) ferrite nanopowder doped with Zn(2+)

This work involved an investigation to ascertain how the substitution of nickel ions for zinc ions affects the structural, morphological and magnetic properties of NiFe(2)O(4) ferrite samples. Ni(1-x)Zn(x)Fe(2)O(4) (x = 0.0, 0.3 0.5, 0.7) powders were prepared by combustion reaction and characterized structurally by X-ray diffraction. The specific surface area of the powders was determined by the nitrogen adsorption method (BET). Magnetization measurements were taken using an alternative gradient magnetometer (AGM), which revealed that the powders prepared by combustion reaction resulted in nanosized particles with a particle size of 18-27 nm. The crystallite size and lattice parameter increased as the concentration of Zn increased. Moreover, augmenting the Zn content in the NiFe(2)O(4) ferrite increased the saturation magnetization and coercive field. (C) 2008 Elsevier B.V. All rights reserved.

Ni-Zn-Sm nanopowder ferrites: Morphological aspects and magnetic properties

Ni-Zn ferrites have been widely used in components for high-frequency range applications due to their high electrical resistivity, mechanical strength and chemical stability. Ni-Zn ferrite nanopowders doped with samarium with a nominal composition of Ni0.5Zn0.5Fe2-xSmxO4 (x = 0.0, 0.05, and 0.1 mol) were obtained by combustion synthesis using nitrates and urea as fuel. The morphological aspects of Ni-Zn-Sm ferrite nanopowders were investigated by X-ray diffraction, nitrogen adsorption by BET, sedimentation, scanning electron microscopy and magnetic properties. The results indicated that the Ni-Zn-Sm ferrite nanopowders were composed of soft agglomerates of nanoparticles with a high surface area (55.8-64.8 m(2)/g), smaller particles (18-20 nm) and nanocrystallite size particles. The addition of samarium resulted in a reduction of all the magnetic parameters evaluated, namely saturation magnetization (24-40 emu/g), remanent magnetization (2.2-3.5 emu/g) and coercive force (99.3-83.3 Oe). (c) 2007 Elsevier B. V. All rights reserved.

Ac and dc magnetotransport properties of the phase-separated La(0.6)Y(0.1)Ca(0.3)MnO(3) manganite

The physical properties of the La(0.6)Y(0.1)Ca(0.3)MnO(3) compound have been investigated, focusing on the magnetoresistance phenomenon studied by both dc and ac electrical transport measurements. X-ray diffraction and scanning electron microscopy analysis of ceramic samples prepared by the sol-gel method revealed that specimens are single phase and have average grain size of similar to 0.5 mu m. Magnetization and 4-probe dc electrical resistivity rho(T,H) experiments showed that a ferromagnetic transition at T(C) similar to 170 K is closely related to a metal-insulator (MI) transition occurring at essentially the same temperature T(MI). The magnetoresistance effect was found to be more pronounced at low applied fields (H <= 2.5 T) and temperatures close to the MI transition. The ac electrical transport was investigated by impedance spectroscopy Z(f,T,H) under applied magnetic field H up to 1 T. The Z(f,T,H) data exhibited two well-defined relaxation processes that exhibit different behaviors depending on the temperature and applied magnetic field. Pronounced effects were observed close to T (C) and were associated with the coexistence of clusters with different electronic and magnetic properties. In addition, the appreciable decrease of the electrical permittivity epsilon`(T,H) is consistent with changes in the concentration of e(g) mobile holes, a feature much more pronounced close to T (C).

Magnetic interaction in exchange-biased bilayers: a first-order reversal curve analysis

The distributions of coercivities and magnetic interactions in a set of polycrystalline Ni(0.8)Fe(0.2)/FeMn bilayers have been determined using the first-order reversal curve (FORC) formalism. The thickness of the permalloy (Py) film was fixed at 10 nm (nominal), while that of the FeMn film varied within the range 0-20 nm. The FORC diagrams of each bilayer displayed two clearly distinguishable regions. The main region was generated by Py particles whose coercivities were enhanced in comparison with those in which the FeMn film was absent (sample O). The minor region was produced by Py particles with coercivities similar to or slightly higher than those of particles in the Py film of sample O. Each sample presented two distributions of interaction fields, one for each region, and both were centred slightly below the exchange-bias field, thus indicating a prevalence of magnetizing interactions. These results are consistent with a grain size distribution in the Py layer and the presence of uncompensated antiferromagnetic moments.

Effect of urea and glycine fuels on the combustion reaction synthesis of Mn-Zn ferrites: Evaluation of morphology and magnetic properties

The goal of this study is to evaluate the influence of the urea and glycine fuels on the synthesis of Mn-Zn ferrite by combustion reaction The morphology and magnetic properties of the resulting powders were investigated. The powders were characterized by X-ray diffraction (XRD), nitrogen adsorption (BET), scanning and transmission electron microscopy (SEM and TEM), and magnetic measurement of M x H curves. The X-lay diffraction patterns indicated that the samples containing urea resulted in the formation of crystalline powders and the presence of hematite as a secondary phase The samples containing glycine presented only the formation of crystalline and monophases (Mn,Zn)Fe(2)O(4). The average crystallite size was 18 and 35 nm and saturation magnetization was 3.6 and 75 emu/g, respectively, for the samples containing urea and glycine. The samples synthesized with glycine fuel showed better magnetic properties for application as soft magnetic devices. (C) 2009 Elsevier B.V All rights reserved

Structural and magnetic properties of chromium-doped ferrite nanopowders

This paper reports on a study of Cr(3+)-doped nanosized Ni-Zn ferrites produced by combustion reaction, and evaluates their morphological and magnetic properties. The powders were characterized by X-ray diffraction (XRD) and SEM and magnetic properties. All the compositions showed the formation of the inverse spinel phase of Ni-Zn ferrite. The average crystallite size ranged from 21 to 26 nm. The saturation magnetization was found to be in the range of 53-43 emu/g. The increase in Cr(3+) concentration in the Ni-Zn ferrite caused a reduction in hysteresis losses and a slight reduction in the saturation magnetization. (C) 2008 Elsevier B.V. All rights reserved.

Magnetic Fluids Based on gamma-Fe(2)O(3) and CoFe(2)O(4) Nanoparticles Dispersed in Ionic Liquids

The disclosure of magnetic ionic liquids (MILs) as stable dispersions of surface modified gamma-Fe(2)O(3) or CoFe(2)O(4) nanoparticles (NPs) in the 1-n-butyl-3-methylimidazolium tetrafluoroborate (BMIBF(4)) ionic liquid is reported. The magnetic NPs were characterized by X-ray powder diffraction, transmission electron microscopy, and Raman spectroscopy. The surface modified NPs have proved to form stable dispersions in BMIBF(4) in the absence of water and behave like a magnetic ionic liquid. The MILs have been characterized by Raman spectroscopy, magnetic measurements, and DSC. The stability of the magnetic NPs in BMIBF(4) is consistently explained by assuming the formation of a semiorganized protective layer composed of supramolecular aggregates in the form of [(BMI)(2)(BF(4))(3)](-). A superparamagnetic behavior and saturation magnetization of ca. 18 emu/g for a sample containing 30% w/w maghemite NPs/BMIBF(4) have been inferred from static and dynamic magnetic measurements. DSC results have shown that the MIL composed of 30% w/w CoFe(2)O(4) NPs/BMIBF(4) remains a liquid phase down to -84 degrees C.