Analysis of the beta-glucoside utilization (bgl) genes of Shigella sonnei: evolutionary implications for their maintenance in a cryptic state

The pattern of expression of the genes involved in the utilization of aryl beta-glucosides such as arbutin and salicin is different in the genus Shigella compared to Escherichia coli. The results presented here indicate that the homologue of the cryptic bgl operon of E. coli is conserved in Shigella sonnei and is the primary system involved in beta-glucoside utilization in the organism. The organization of the bgl genes in 5. sonnei is similar to that of E. coli; however there are three major differences in terms of their pattern of expression. (i) The bglB gene, encoding phospho-beta-glucosidase B, is insertionally inactivated in 5. sonnei. As a result, mutational activation of the silent bgl promoter confers an Arbutin-positive (Arb(+)) phenotype to the cells in a single step; however, acquiring a Salicin-positive (Sal(+)) phenotype requires the reversion or suppression of the bglB mutation in addition. (ii) Unlike in E. coli, a majority of the activating mutations (conferring the Arb(+) phenotype) map within the unlinked hns locus, whereas activation of the E. coli bgl operon under the same conditions is predominantly due to insertions within the bglR locus. (iii) Although the bgl promoter is silent in the wild-type strain of 5. sonnei (as in the case of E. coli), transcriptional and functional analyses indicated a higher basal level of transcription of the downstream genes. This was correlated with a 1 bp deletion within the putative Rho-independent terminator present in the leader sequence preceding the homologue of the bglG gene. The possible evolutionary implications of these differences for the maintenance of the genes in the cryptic state are discussed.

Photocytotoxicity and DNA cleavage activity of L-arg and L-lys Schiff base oxovanadium(IV) complexes having phenanthroline bases

Oxovanadium(IV) complexes [VO(sal-argH)(B)] Cl (1-3) and [VO(sal-lysH)(B)] Cl (4-6), where sal-argH2 and sal-lysH(2) are N-salicylidene-L-arginine and N-salicylidene-L-lysine Schiff bases and B is a phenanthroline base, viz. 1,10-phenanthroline (phen in 1 and 4); dipyrido[3,2-d: 2', 3'-f] quinoxaline (dpq in 2 and 5) and dipyrido[3,2-a: 2', 3'-c] phenazine (dppz in 3 and 6), have been prepared, characterized and their DNA photocleavage activity studied. Complex 1, characterized by X-ray crystallography, shows the presence of a vanadyl group in VIVO3N3 coordination geometry with a tridentate Schiff base having a pendant guanidinium moiety and bidentate phen ligand. The complexes exhibit a d-d band at similar to 715 nm in 20% DMF-Tris-HCl buffer. The complexes are redox active showing cathodic and anodic responses near -1.0 V and 0.85 V (vs. SCE) for the V(IV)-V(III) and V(V)-V(IV) couples, respectively, in DMF-Tris-HCl buffer. The complexes bind to calf thymus DNA giving Kb values in the range of 3.8 x 10(4) to 1.6 x 10(5) M-1. Thermal denaturation and viscosity data suggest DNA groove binding nature of the complexes. The complexes do not show any `chemical nuclease'' activity in dark in the presence of 3-mercaptopropionic acid or H2O2. The dpq and dppz complexes are efficient photocleavers of plasmid DNA in UV-A (365 nm) and red light (676 nm) via singlet oxygen pathway. The dppz complexes exhibit photocytotoxicity in HeLa cancer cells giving IC50 values of 15.4 mu M for 3 and 17.5 mu M for 6 in visible light while being non-toxic in dark giving IC50 values of > 100 mu M.

Synthesis and Studies of Pb0.76Ca0.24TiO3 Nanoparticles Derived by Sol-Gel

Pb0.76Ca0.24TiO3 (PCT24) nanoparticles were synthesized by modified sal gel method and characterized by a number of experimental techniques such as X-ray diffraction, TGA-DTA, FTIR and transmission electron microscopy equipped with energy-dispersive X-ray spectroscopy (EDX). X-ray diffraction (XRD) and selected-area electron diffraction (SAED) investigations demonstrated that the postannealed (650 degrees C for 1 h) PCT24 nanoparticles have tetragonal perovskite crystal structure. TEM have been employed to characterize the morphology, structure and composition of the as prepared nanoparticles. Dielectric results indicates the evidence for relaxor type behavior while observed leaky ferroelectric loops may be because of the defects such as grain boundaries and the pores in the sample as the sample was not heated at higher temperature, to retain the nanosize dimension of the particles.

Diverse pathways for salicin utilization in Shigella sonnei and Escherichia coli carrying an impaired bgl operon

Utilization of the aryl-beta-glucosides salicin or arbutin in most wild-type strains of E. coli is achieved by a single-step mutational activation of the bgl operon. Shigella sonnei, a branch of the diverse E. coli strain tree, requires two sequential mutational steps for achieving salicin utilization as the bglB gene, encoding the phospho-beta-glucosidase B, harbors an inactivating insertion. We show that in a natural isolate of S. sonnei, transcriptional activation of the gene SSO1595, encoding a phospho-beta-glucosidase, enables salicin utilization with the permease function being provided by the activated bgl operon. SSO1595 is absent in most commensal strains of E. coli, but is present in extra-intestinal pathogens as bgcA, a component of the bgc operon that enables beta-glucoside utilization at low temperature. Salicin utilization in an E. coli bglB laboratory strain also requires a two-step activation process leading to expression of BglF, the PTS-associated permease encoded by the bgl operon and AscB, the phospho-beta-glucosidase B encoded by the silent asc operon. BglF function is needed since AscF is unable to transport beta-glucosides as it lacks the IIA domain involved in phopho-relay. Activation of the asc operon in the Sal(+) mutant is by a promoter-up mutation and the activated operon is subject to induction. The pathway to achieve salicin utilization is therefore diverse in these two evolutionarily related organisms; however, both show cooperation between two silent genetic systems to achieve a new metabolic capability under selection.

Synthesis and structural characterization of perovskite 0.65Pb(Mg1/3Nb2/3)O-3-0.35PbTiO(3) nanotubes

We report the synthesis and structural characterization of 0.65Pb(Mg1/3Nb2/3)O-3-0.35PbTiO(3) (PMN-PT) nanotubes prepared by a novel sal-gel template method. X-ray diffraction (XRD) and selected-area electron diffraction (SAED) investigations demonstrated that the postannealed (650 degrees C for 1 h) PMN-PT nanotubes were polycrystalline with perovskite crystal structure. The field emission scanning electron microscope (FE-SEM) shows that as prepared PMN-PT nanotubes were hollow with diameter to be about 200 nm. High resolution transmission electron microscope (HRTEM) analysis confirmed that the obtained PMN-PT nanotubes made up of nanoparticles (10-20 nm) which were randomly aligned in the nanotubes. Energy-dispersive X-ray spectroscopy (EDX) analysis confirmed the stoichiometric 0.65Pb(Mg1/3Nb2/3)O-3-0.35PbTiO(3). The possible formation mechanism of PMN-PT nanotubes was proposed at the end. (C) 2011 Elsevier B.V. All rights reserved.

PAMAM Dendrimer-Drug Interactions: Effect of pH on the Binding and Release Pattern

Understanding the dendrimer-drug interaction is of great importance to design and optimize the dendrimer-based drug delivery system. Using atomistic molecular dynamics (MD) simulations, we have analyzed the release pattern of four ligands (two soluble drugs, namely, salicylic acid (Sal), L-alanine (Ala), and two insoluble drugs, namely, phenylbutazone (Pbz) and primidone (Prim)), which were initially encapsulated inside the ethylenediamine (EDA) cored polyamidoamine (PAMAM) dendrimer using the docking method. We have computed the potential of mean force (PMF) variation with generation 5 (G5)-PAMAM dendrimer complexed with drug molecules using umbrella sampling. From our calculated PMF values, we observe that soluble drugs (Sal and Ala) have lower energy barriers than insoluble drugs (Pbz and Prim). The order of ease of release pattern for these drugs from G5 protonated PAMAM dendrimer was found to be Ala > Sal > Prim > Pbz. In the case of insoluble drugs (Prim and Pbz), because of larger size, we observe much nonpolar contribution, and thus, their larger energy barriers can be reasoned to van der Waals contribution. From the hydrogen bonding analysis of the four PAMAM drug complexes under study, we found intermolecular hydrogen bonding to show less significant contribution to the free energy barrier. Another interesting feature appears while calculating the PMF profile of G5NP (nonprotonated)-PAMAM Pbz and G5NP (nonprotonated)-PAMAM-Sal complex. The PMF was found to be less when the drug is bound to nonprotonated dendrimer compared to the protonated dendrimer. Our results suggest that encapsulation of the drug molecule into the host PAMAM dendrimer should be carried out at higher pH values (near pH 10). When such complex enters the human body, the pH is around 7.4 and at that physiological pH, the dendrimer holds the drug tightly. Hence the release of drug can occur at a controlled rate into the bloodstream. Thus, our findings provide a microscopic picture of the encapsulation and controlled release of drugs in the case of dendrimer-based host-guest systems.

Enhancing the magnetic characteristics of BiFeO3 nanoparticles by Ca, Ba co-doping

Multiferroic nanoparticles (NPs) of pristine and Ca, Ba co-doped BiFeO3 were synthesized by a facile sal gel route. Co-doping was done by fixing the total dopant concentration at 5 mol% and then the relative concentrations of Ca and Ba was varied. Structural, optical and magnetic properties of the NPs were investigated using different techniques. UV-Vis absorption spectra of BiFeO3 NPs showed a substantial blue shift of similar to 100 nm (530 nm -> 430 nm) on Ca. Ba co-doping which corresponds to increase in band gap by 0.5 eV. Fe-57 Mossbauer spectroscopy confirmed that iron is present only in 3(+) valence state in all co-doped samples. The coercive field increased by 18 times for Bi0.95Ca0.01Ba0.04FeO3 samples, which is the maximum enhancement, observed amongst all the 5 mol% doped samples. At the equimolar (2.5 mol % each) concentration of co-dopants, the coercive field shows a significant enhancement of about 9 times (220 Oe -> 2014 Oe) with concomitant increase in saturation magnetization by 7 times. Thus, equimolar co-doping causes simultaneous enhancement of the twin aspects of magnetic properties thereby making them better suited for device applications. (C) 2012 Elsevier B.V. All rights reserved.

Metal doped nanosized titania used for the photocatalytic degradation of rhodamine B dye under visible-light

Metal-doped anatase nanosized titania photocatalysts were successfully synthesized using a sal gel process. Different amounts of the dopants (0.2, 0.4, 0.6, 0.8 and 1.0%) of the metals (Ag, Ni, Co and Pd) were utilized. The UV-Vis spectra (solid state diffuse reflectance spectra) of the doped nanoparticles exhibited a red shift in the absorption edge as a result of metal doping. The metal-doped nanoparticles were investigated for their photocatalytic activity under visible-light irradiation using Rhodamine B (Rh B) as a control pollutant. The results obtained indicate that the metal-doped titania had the highest activity at 0.4% metal loading. The kinetic models revealed that the photodegradation of Rh B followed a pseudo first order reaction. From ion chromatography (IC) analysis the degradation by-products Rhodamine B fragments were found to be acetate, chloride, nitrite, carbonate and nitrate ions.

Mitochondria-Targeting Oxidovanadium(IV) Complex as a Near-IR Light Photocytotoxic Agent

Oxidovanadium(IV) complexes VO(L-1)(phen)]Cl (1) and VO(L-2)(L-3)]Cl (2), in which HL1 is 2-{(benzimidazol-2-yl)methylimino]-methyl}phenol (sal-ambmz), HL2 is 2-({1-(anthracen-9-yl)methyl]-benzimidazol-2-yl}methylimino)-met hyl]phenol (sal-an-ambmz), phen is 1,10-phenanthroline and L-3 is dipyrido3,2-a:2,3-c]phenazine (dppz) conjugated to a Gly-Gly-OMe dipeptide moiety, were prepared, characterized, and their DNA binding, photoinduced DNA-cleavage, and photocytotoxic properties were studied. Fluorescence microscopy studies were performed by using complex 2 in HeLa and HaCaT cells. Complex 1, structurally characterized by X-ray crystallography, has a vanadyl group in VO2N4 core with the VO2+ moiety bonded to N,N-donor phen and a N,N,O-donor Schiff base. Complex 2, having an anthracenyl fluorophore, showed fluorescence emission bands at 397, 419, and 443nm. The complexes are redox-active exhibiting the V(IV)/V(III) redox couple near -0.85V versus SCE in DMF 0.1M tetrabutylammonium perchlorate (TBAP). Complex 2, having a dipeptide moiety, showed specific binding towards poly(dAdT)(2) sequence. The dppz-Gly-Gly-OMe complex showed significant DNA photocleavage activity in red light of 705nm through a hydroxyl radical ((OH)-O-.) pathway. Complex 2 showed photocytotoxicity in HaCaT and HeLa cells in visible light (400-700nm) and red light (620-700nm), however, the complex was less toxic in the dark. Fluorescence microscopy revealed the localization of complex 2 primarily in mitochondria. Apoptosis was found to occur inside mitochondria (intrinsic pathway) caused by ROS generation.

Mesoporous bioactive glass and glass-ceramics: Influence of the local structure on in vitro bioactivity

Mesoporous quaternary bioactive glasses and glass-ceramic with alkali-alkaline-earth oxide were successfully synthesized by using non-ionic block copolymer P123 and evaporation induced self assembly (EISA) process followed by acid treatment assisted sal-gel method. As prepared samples has been characterized for the structural, morphological and textural properties with the various analytical techniques. Glass dissolution/ion release rate in simulated body fluid (SBF) was monitored by inductively coupled plasma (ICP) emission spectroscopy, whereas the formation of apatite phase and its crystallization at the glass and glass-ceramic surface was examined by structural, textural and microscopic probes. The influence of alkaline-earth oxide content on the glass structure followed by textural property has become more evident. The pristine glass samples exhibit a wormhole-like mesoporous structure, whereas the glass-ceramic composition is found to be in three different phases, namely crystalline hydroxyapatite, wollastonite and a residual glassy phase as observed in Cerabone (R) A/W. The existence of calcium orthophosphate phase is closely associated with the pore walls comprising nanometric-sized ``inclusions''. The observed high surface area in conjunction with the structural features provides the possible explanation for experimentally observed enhanced bioactivity through the easy access of ions to the fluid. On the other hand, presence of multiple phases in glass-ceramic sample inhibits or delays the kinetics of apatite formation. (C) 2013 Elsevier Inc. All rights reserved.

Effect of Ni-Zr codoping on dielectric and magnetic properties of SrFe12O19 via sol-gel route

Nanocrystalline strontium hexaferrites SrFe12-2x (Ni2+-Zr4+)(x)O-19] nanoparticles were successfully synthesized by sal gel process. For densification the powders were sintered at 950 degrees C/4 h. The sintered samples were characterized by X-ray diffraction (XRD), surface area measurement, and field emission scanning electron microscope (FESEM). The lattice parameter a is almost constant but c increased with x upto 0.8 and then decreased. The frequency dependent complex permittivity (epsilon and epsilon `' and permeability (mu' and mu `') and magnetic properties such as saturation magnetization (M-s), coercive field (H-c) were studied. If is observed that saturation magnetization increased gradually from 57.82 emuig to 67.2 emufg as x increased from 0.2 to 0.4 and then decreased from 672 emufg to 31.63 ernufg for x=1.0. In present study, x=0.4 shows high value of M-s 67.2 emu/g. The real part of permittivity (epsilon') remains constant upto a frequency 1 GHz and increases further with an increase of frequency, a resonance and anti resonance peak was observed above 1 GHz for all the samples. In real part of permeability (mu') the relaxation frequency is observed above 1 GHz for all the samples and it is attributed to the domain wall motion. It is well known that the permeability for polycrystalline ferrites can be described as the superposition of two different magnetizing mechanisms: spin rotation and domain wall motion. These low coercive strontium hexaferrites are suitable for magnetic recording applications in hard disks, floppy disks, video tapes, etc. (C) 2015 Elsevier B.V. All rights reserved.

Nest site characterization of sympatric hornbills in a tropical dry forest

Hornbills, among the largest and most threatened tropical frugivores, provide important seed dispersal services. Hornbill nest site characteristics are known primarily from wet tropical forests. Nests of the Indian grey hornbill Ocyceros birostris and Oriental pied hornbill Anthracoceros albirostris were characterized in a tropical dry forest. Despite A. albirostris being twice the size of O. birostris, few of the nest cavity attributes were different. A. albirostris nests were surrounded by higher proportion of mixed forest and lower sal forest compared to O. birostris. In this landscape, the larger A. albirostris may prefer to nest in sites with more food plants compared to the smaller O. birostris.

Iron(III) salicylates of dipicolylamine bases showing photo-induced anticancer activity and cytosolic localization

An iron(III) salicylate having a dipicolylamine base (andpa) with a photoactive anthracenyl moiety is prepared, characterized, and studied for its photo-induced anticancer activity and cellular localization in HeLa and MCF-7 cells. Its phenyl analogue is structurally characterized by X-ray crystallography. The complex has a ternary structure in which the dipicolylamine ligand and salicylic acid in dianionic form (sal) display respective tridentate and bidentate mode of coordination in Fe(sal)(phdpa)Cl] (1). Complex Fe(sal)(andpa)Cl] (2) having a pendant anthracenyl moiety shows significant photocytotoxicity in visible light (400-700 nm) giving IC50 values of 8.6 +/- 0.7 and 3.4 +/- 0.9 mu M in HeLa and MCF-7 cells, while being essentially nontoxic in the dark (IC50 > 100 mu M). The complex shows cytosolic localization in the cancer cells. Formation of hydroxyl radicals ((OH)-O-center dot) as the reactive oxygen species is evidenced from the pUC19 DNA photocleavage studies. (C) 2015 Elsevier Ltd. All rights reserved.

Evaluación de la inclusión de yuca (Manihot esculenta cranz) y suero en la alimentación de cerdos en las etapas de desarrollo y engorde

Se realizó un experimento con 30 cerdos comerciales en las etapas de desarrollo y engorde, con una duración de 120 días (60 días por etapa) con el objetivo de evaluar el efecto de la inclusión de yuca y suero en la alimentación. Sobre consumo, ganancia medía diaria (GMD), conversión alimenticia y utilidad económica. Los cerdos fueron asignados aleatoriamente en 3 grupos de 10 cerdos cada uno, de pesos similares con 60 días de edad, utilizándose un Diseño Completo al Azar (D.C.A. ). Se encontró diferencias significativas (P<0.05) en las categorías de desarrollo y engorde en cuanto a ganancia medía diaria del tratamiento T 1 respecto a los tratamientos T2 y T3. Las raciones experimentales estaban constituidas por: T1 (testigo) concentrado comercial, T2 base (50% maíz., 50% semolina y sal) y suero y el T3 la misma base, suero y yuca. En la etapa de desarrollo los consumos de alimento, ganancia media diaria y conversión alimenticia promedio por cerdo fueron de: 63.48, 189.57 y 218.45 kg; 384.33, 174.33 y 158.33 gramos/día; 2.75, 19.95 y 20.88 para T1, T2 y T3 respectivamente. En la etapa de engorde, los consumos de alimento, ganancia media diaria y conversión alimenticia promedia por cerdo fueron de: 164.98, 343.44 y 355.87 kg; 822.03, 398.65 y 328.80 gramos/día; 3.34, 14.36 y 18.03. El análisis económico evidencia que las mejores utilidades se obtuvieron con el T2 en la etapa de engorde con C$90.61/cerdo. Se concluye que se puede suministrar raciones para la alimentación de cerdos en engorde con subproductos lácteos y agrícolas con el fin de disminuir los costos por alimento.

Aplicación de algunas prácticas de manejo y su efecto en el anestro en vacas del Municipio de San Dionisio Matagalpa

El presente estudio realizado en el municipio de San Dionisia Departamento de Matagalpa, a travéz de un estudio retrospectivo del Banco de datos de seguimiento a fincas que PRODESSA venía realizando desde 1988 en 6 comunidades, permitió caracterizar el ganado manejado en pequeñas fincas encontrándose, un rango promedio de producción de leche de 3 a 5.3 litros y un rango promedio de lactación entre 7.7 a 11.1 meses. La alimentación principal es a base de pasto jaragua (Hyparrhenia ruffa), rastrojos de csecha, leguminosas naturales, en menor grado el pasto Taiwán (Pennisetum purpureum), pasto estrella, (Cynodon nlenfuensis), y suministro de sal común. En salud animal las actividades realizadas son: vacunación contra Ántrax y Pierna Negra, la realizan 2 veces en el año el 100% de productores, control de ectoparásitos 12 baños promedio anuales el 100% de productores, desparasitación interna, 2 veces en el año el 24% de productores, una vez al año el 57% y el 11% no lo realizan, la vitaminación, el 60% realiza una por año, el 12% 2 por año y el 28% de productores no vitaminan. Las pequeñas fincas presentan áreas no mayores de 5 mz. de tierra el 46.75%, el 33.76% con áreas no mayores de 10 mz. de terreno y el 19.43% con áreas mayores de 10 mz. de tierra. Además se definieron siete prácticas de manejo y se evaluó su efecto en vacas con anestro obteniéndose los siguientes resultados: la primera práctica consistió en la suplementación alimenticia a base de maíz triturado (A), desparasitación interna con levamisol (D) y masajes estimulantes (M) a 33 vacas representando el 100% de los animales, manifestando celo al final de la práctica el 9.09%. La segunda práctica se aplicó a un total de 16 vacas que, representan el 48.48% del total inicial, a estas se les suministró vitamina AD,E (V), de las cuales presentaron celo el 21.21%. La tercera práctica se realizó con 14 vacas que representan el 42.42% del cohorte, a las que se les suministró minerales (Mi) aplicando Tonofosfan, presentó celo el 24.24% del total inicial. La cuarta práctica se aplicó a 9 vacas que representan el 27.27% del cohorte, que posterior a la aplicación de la primera y la segunda práctica se les suministró minerales, presentando celo el 12.12% del total inicial. La quinta práctica se aplicó a un total de 6 vacas que representaron el 18.18% del total, a estas se suministró vitamina AD,E, presentó celo el 15.15% del total inicial. La sexta práctica se ejecutó con 5 vacas representando el 15.15%, se les suministro hormonas, a 4 de ellas por presencia de cuerpo lúteo persistente, se les aplicó la hormona Prosolvin y a una Por presencia de quiste folicular se le aplicó la hormona Foligon, de las cuales presentó celo el 3.03%. La séptima práctica se realizó con una vaca, que representa el 3.03% del total inicial se le aplicó la hormona Foligon por presencia de quiste folicular, no logrando esta vaca presentar celo con esta última práctica. Al comparar las prácticas entre ellas se obtuvieron los siguientes resultados: Se encontraron diferencias significativas (P<0.05) al comparar la primera práctica con la segunda, tercera, cuarta y quinta práctica, mayoritariamente hacia la segunda, tercera, cuarta y quinta práctica, de igual manera al comparar la quinta con la sexta y séptima práctica se encontraron diferencias significativas (P<0.05) con mayor efecto a la quinta práctica.