Histologia da embriogênese somática induzida em embriões de sementes maduras de Urochloa brizantha apomítica

O objetivo deste trabalho foi descrever o processo de embriogênese somática em Urochloa brizantha cv. Marandu (Syn. Brachiaria brizantha cv. Marandu) e fornecer subsídios para o aprimoramento dos métodos de cultura de tecidos e transformação genética. Calos embriogênicos foram obtidos por indução em embriões isolados de sementes maduras, e cultivados in vitro, em meio de cultura que continha ácido 2,4‑diclorofenoxiacético, 6‑benzilaminopurina e caseína hidrolisada. Plântulas foram regeneradas a partir dos calos embriogênicos, na presença de ácido naftalenoacético e cinetina. Esse processo foi descrito morfologicamente por observações em microscopia de luz de secções seriadas semifinas de tecidos fixados, ao longo do processo de regeneração, em FAA [formaldeído (40%): ácido acético glacial: etanol (50%), a 5:5:90 v/v/v]. Os embriões das sementes de U. brizantha cv. Marandu não têm epiblasto e são classificados como do tipo panicoide. Nas condições estabelecidas de cultura in vitro, calos embriogênicos e embriões somáticos de U. brizantha cv. Marandu, desenvolvem-se a partir de células meristemáticas do escutelo

Analytic Description of Critical Point Actinides in a Transition from Octupole Deformation to Octupole Vibrations

An analytic collective model in which the relative presence of the quadrupole and octupole deformations is determined by a parameter (phi_0), while axial symmetry is obeyed, is developed. The model [to be called the analytic quadrupole octupole axially symmetric model (AQOA)] involves an infinite well potential, provides predictions for energy and B(EL) ratios which depend only on phi_0, draws the border between the regions of octupole deformation and octupole vibrations in an essentially parameter-independent way, and describes well 226-Th and 226-Ra, for which experimental energy data are shown to suggest that they lie close to this border. The similarity of the AQOA results with phi_0=45 degrees for ground state band spectra and B(E2) transition rates to the predictions of the X(5) model is pointed out. Analytic solutions are also obtained for Davidson potentials, leading to the AQOA spectrum through a variational procedure.Comment: LaTeX, 27 pages, including 14 postscript figure

Sequence of Potentials Lying Between the U(5) and X(5) Symmetries

Starting from the original collective Hamiltonian of Bohr and separating the beta and gamma variables as in the X(5) model of Iachello, an exactly soluble model corresponding to a harmonic oscillator potential in the beta-variable (to be called X(5)-$\beta^2$) is constructed. Furthermore, it is proved that the potentials of the form $\beta^{2n}$ (with n being integer) provide a ``bridge'' between this new X(5)-$\beta^2$ model (occuring for n=1) and the X(5) model (corresponding to an infinite well potential in the beta-variable, materialized for n going to infinity. Parameter-free (up to overall scale factors) predictions for spectra and B(E2) transition rates are given for the potentials $\beta^2$, $\beta^4$, $\beta^6$, $\beta^8$, corresponding to E(4)/E(2) ratios of 2.646, 2.769, 2.824, and 2.852 respectively, compared to the E(4)/E(2) ratios of 2.000 for U(5) and 2.904 for X(5). Hints about nuclei showing this behaviour, as well as about potentials ``bridging'' the X(5) symmetry with SU(3) are briefly discussed.Comment: 18 pages, LaTeX, 5 postscript figure

Exactly separable version of the Bohr Hamiltonian with the Davidson potential

An exactly separable version of the Bohr Hamiltonian is developed using a potential of the form u(beta)+u(gamma)/beta^2, with the Davidson potential u(beta)= beta^2 + beta_0^4/beta^2 (where beta_0 is the position of the minimum) and a stiff harmonic oscillator for u(gamma) centered at gamma=0. In the resulting solution, called exactly separable Davidson (ES-D), the ground state band, gamma band and 0_2^+ band are all treated on an equal footing. The bandheads, energy spacings within bands, and a number of interband and intraband B(E2) transition rates are well reproduced for almost all well-deformed rare earth and actinide nuclei using two parameters (beta_0, gamma stiffness). Insights regarding the recently found correlation between gamma stiffness and the gamma-bandhead energy, as well as the long standing problem of producing a level scheme with Interacting Boson Approximation SU(3) degeneracies from the Bohr Hamiltonian, are also obtained.Comment: 35 pages, 11 postscript figures, LaTe

Nuclear collective motion with a coherent coupling interaction between quadrupole and octupole modes

A collective Hamiltonian for the rotation-vibration motion of nuclei is considered, in which the axial quadrupole and octupole degrees of freedom are coupled through the centrifugal interaction. The potential of the system depends on the two deformation variables $\beta_2$ and $\beta_3$. The system is considered to oscillate between positive and negative $\beta_3$-values, by rounding an infinite potential core in the $(\beta_2,\beta_3)$-plane with $\beta_2>0$. By assuming a coherent contribution of the quadrupole and octupole oscillation modes in the collective motion, the energy spectrum is derived in an explicit analytic form, providing specific parity shift effects. On this basis several possible ways in the evolution of quadrupole-octupole collectivity are outlined. A particular application of the model to the energy levels and electric transition probabilities in alternating parity spectra of the nuclei $^{150}$Nd, $^{152}$Sm, $^{154}$Gd and $^{156}$Dy is presented.Comment: 25 pages, 13 figures. Accepted in Phys. Rev.

Structure, morphology, adhesion and in vitro biological evaluation of antibacterial multi-layer HA-Ag/SiO2/TiN/Ti coatings obtained by RF magnetron sputtering for biomedical applications

[EN] Biocompatible and antibacterial multi-layer coatings of hydroxyapatite (HA)-Ag/SiO2/TiN/Ti were obtained on the Ti-6Al-4V alloy, by means of the magnetron sputtering technique. During characterization of the coatings, the chemical composition was evaluated by energy dispersive X-ray spectroscopy and the phase analysis was carried out by X-ray diffraction. The morphology of the coatings was observed by field emission scanning electron microscopy, while transmission electron microscopy was used to appreciate their structure. The adhesion of the coatings to the substrate was evaluated by micro scratch test. The in vitro biological response was evaluated in terms of cytotoxicity, adhesion and differentiation of mouse mesenchymal stem cells, as well as adhesion and bacterial viability of Staphylococcus aureus strain. Through the compositional study carried out, the deposition of the HA phase was verified, with a Ca/P ratio close to 1.67 and the characteristic diffraction peaks of this compound. The structural study of the coatings evidenced the obtention of multi-layer architectures. The use of an intermediate SiO2/TiN/Ti trilayer was found to improve adhesion between HA-Ag and the substrate by 84%. Finally, the in vitro biological tests carried out indicated a potentially non-toxic character in the coatings. Additionally, an antibacterial effect was registered at low concentrations of Ag (3.0.co;2-3Lalueza, P., Monzón, M., Arruebo, M., & Santamaría, J. (2011). Bactericidal effects of different silver-containing materials. Materials Research Bulletin, 46(11), 2070-2076. doi:10.1016/j.materresbull.2011.06.041Peetsch, A., Greulich, C., Braun, D., Stroetges, C., Rehage, H., Siebers, B., … Epple, M. (2013). Silver-doped calcium phosphate nanoparticles: Synthesis, characterization, and toxic effects toward mammalian and prokaryotic cells. Colloids and Surfaces B: Biointerfaces, 102, 724-729. doi:10.1016/j.colsurfb.2012.09.040Yanovska, A. A., Stanislavov, A. S., Sukhodub, L. B., Kuznetsov, V. N., Illiashenko, V. Y., Danilchenko, S. N., & Sukhodub, L. F. (2014). Silver-doped hydroxyapatite coatings formed on Ti–6Al–4V substrates and their characterization. Materials Science and Engineering: C, 36, 215-220. doi:10.1016/j.msec.2013.12.011DeVasConCellos, P., Bose, S., Beyenal, H., Bandyopadhyay, A., & Zirkle, L. G. (2012). Antimicrobial particulate silver coatings on stainless steel implants for fracture management. Materials Science and Engineering: C, 32(5), 1112-1120. doi:10.1016/j.msec.2012.02.020VALLETREGI, M. (2004). Calcium phosphates as substitution of bone tissues. Progress in Solid State Chemistry, 32(1-2), 1-31. doi:10.1016/j.progsolidstchem.2004.07.001Surmenev, R. A., Surmeneva, M. A., Evdokimov, K. E., Pichugin, V. F., Peitsch, T., & Epple, M. (2011). The influence of the deposition parameters on the properties of an rf-magnetron-deposited nanostructured calcium phosphate coating and a possible growth mechanism. Surface and Coatings Technology, 205(12), 3600-3606. doi:10.1016/j.surfcoat.2010.12.039Surmeneva, M. A., Sharonova, A. A., Chernousova, S., Prymak, O., Loza, K., Tkachev, M. S., … Surmenev, R. A. (2017). Incorporation of silver nanoparticles into magnetron-sputtered calcium phosphate layers on titanium as an antibacterial coating. Colloids and Surfaces B: Biointerfaces, 156, 104-113. doi:10.1016/j.colsurfb.2017.05.016Mohseni, E., Zalnezhad, E., Bushroa, A. R., Abdel Magid Hamouda, Goh, B. T., & Yoon, G. H. (2015). Ti/TiN/HA coating on Ti–6Al–4V for biomedical applications. Ceramics International, 41(10), 14447-14457. doi:10.1016/j.ceramint.2015.07.081Ghasemi, S., Shanaghi, A., & Chu, P. K. (2017). Nano mechanical and wear properties of multi-layer Ti/TiN coatings deposited on Al 7075 by high-vacuum magnetron sputtering. Thin Solid Films, 638, 96-104. doi:10.1016/j.tsf.2017.07.049Hamdi, D. A., Jiang, Z.-T., No, K., Rahman, M. M., Lee, P.-C., Truc, L. N. T., … Dlugogorski, B. Z. (2019). Biocompatibility study of multi-layered hydroxyapatite coatings synthesized on Ti-6Al-4V alloys by RF magnetron sputtering for prosthetic-orthopaedic implant applications. Applied Surface Science, 463, 292-299. doi:10.1016/j.apsusc.2018.08.157Qi, J., Yang, Y., Zhou, M., Chen, Z., & Chen, K. (2019). Effect of transition layer on the performance of hydroxyapatite/titanium nitride coating developed on Ti-6Al-4V alloy by magnetron sputtering. Ceramics International, 45(4), 4863-4869. doi:10.1016/j.ceramint.2018.11.183Lenis, J. A., Hurtado, F. M., Gómez, M. A., & Bolívar, F. J. (2019). Effect of thermal treatment on structure, phase and mechanical properties of hydroxyapatite thin films grown by RF magnetron sputtering. Thin Solid Films, 669, 571-578. doi:10.1016/j.tsf.2018.11.045Lenis, J. A., Gómez, M. A., & Bolívar, F. J. (2019). Effect of deposition temperature and target-substrate distance on the structure, phases, mechanical and tribological properties of multi-layer HA-Ag coatings obtained by RF magnetron sputtering. Surface and Coatings Technology, 378, 124936. doi:10.1016/j.surfcoat.2019.124936Sofronia, A. M., Baies, R., Anghel, E. M., Marinescu, C. A., & Tanasescu, S. (2014). Thermal and structural characterization of synthetic and natural nanocrystalline hydroxyapatite. Materials Science and Engineering: C, 43, 153-163. doi:10.1016/j.msec.2014.07.023Lenis, J. A., Bejarano, G., Rico, P., Ribelles, J. L. G., & Bolívar, F. J. (2019). Development of multilayer Hydroxyapatite - Ag/TiN-Ti coatings deposited by radio frequency magnetron sputtering with potential application in the biomedical field. Surface and Coatings Technology, 377, 124856. doi:10.1016/j.surfcoat.2019.06.097Lenis, J. A., Toro, L. J., & Bolívar, F. J. (2019). Multi-layer bactericidal silver - calcium phosphate coatings obtained by RF magnetron sputtering. Surface and Coatings Technology, 367, 203-211. doi:10.1016/j.surfcoat.2019.03.038Valverde, A., Pérez-Álvarez, L., Ruiz-Rubio, L., Pacha Olivenza, M. A., García Blanco, M. B., Díaz-Fuentes, M., & Vilas-Vilela, J. L. (2019). Antibacterial hyaluronic acid/chitosan multilayers onto smooth and micropatterned titanium surfaces. Carbohydrate Polymers, 207, 824-833. doi:10.1016/j.carbpol.2018.12.039Surmeneva, M. A., Chaikina, M. V., Zaikovskiy, V. I., Pichugin, V. F., Buck, V., Prymak, O., … Surmenev, R. A. (2013). The structure of an RF-magnetron sputter-deposited silicate-containing hydroxyapatite-based coating investigated by high-resolution techniques. Surface and Coatings Technology, 218, 39-46. doi:10.1016/j.surfcoat.2012.12.023Nelea, V., Morosanu, C., Iliescu, M., & Mihailescu, I. N. (2003). Microstructure and mechanical properties of hydroxyapatite thin films grown by RF magnetron sputtering. Surface and Coatings Technology, 173(2-3), 315-322. doi:10.1016/s0257-8972(03)00729-1Ding, S.-J., Ju, C.-P., & Lin, J.-H. C. (1999). Characterization of hydroxyapatite and titanium coatings sputtered on Ti-6Al-4V substrate. Journal of Biomedical Materials Research, 44(3), 266-279. doi:10.1002/(sici)1097-4636(19990305)44:33.0.co;2-4Ivanova, A. A., Surmeneva, M. A., Tyurin, A. I., Pirozhkova, T. S., Shuvarin, I. A., Prymak, O., … Surmenev, R. A. (2016). Fabrication and physico-mechanical properties of thin magnetron sputter deposited silver-containing hydroxyapatite films. Applied Surface Science, 360, 929-935. doi:10.1016/j.apsusc.2015.11.087Contreras Romero, E., Cortínez Osorio, J., Talamantes Soto, R., Hurtado Macías, A., & Gómez Botero, M. (2019). Microstructure, mechanical and tribological performance of nanostructured TiAlTaN-(TiAlN/TaN)n coatings: Understanding the effect of quaternary/multilayer volume fraction. Surface and Coatings Technology, 377, 124875. doi:10.1016/j.surfcoat.2019.07.086Deligianni, D. (2001). Effect of surface roughness of the titanium alloy Ti–6Al–4V on human bone marrow cell response and on protein adsorption. Biomaterials, 22(11), 1241-1251. doi:10.1016/s0142-9612(00)00274-xZareidoost, A., Yousefpour, M., Ghaseme, B., & Amanzadeh, A. (2012). The relationship of surface roughness and cell response of chemical surface modification of titanium. Journal of Materials Science: Materials in Medicine, 23(6), 1479-1488. doi:10.1007/s10856-012-4611-9Surmeneva, M. A., Tyurin, A. I., Mukhametkaliyev, T. M., Pirozhkova, T. S., Shuvarin, I. A., Syrtanov, M. S., & Surmenev, R. A. (2015). Enhancement of the mechanical properties of AZ31 magnesium alloy via nanostructured hydroxyapatite thin films fabricated via radio-frequency magnetron sputtering. Journal of the Mechanical Behavior of Biomedical Materials, 46, 127-136. doi:10.1016/j.jmbbm.2015.02.025Quirama, A., Echavarría, A. M., Meza, J. M., Osorio, J., & Bejarano G, G. (2017). Improvement of the mechanical behavior of the calcium phosphate coatings deposited onto Ti6Al4V alloy using an intermediate TiN/TiO2 bilayer. Vacuum, 146, 22-30. doi:10.1016/j.vacuum.2017.09.024Surmeneva, M. A., Kleinhans, C., Vacun, G., Kluger, P. J., Schönhaar, V., Müller, M., … Surmenev, R. A. (2015). Nano-hydroxyapatite-coated metal-ceramic composite of iron-tricalcium phosphate: Improving the surface wettability, adhesion and proliferation of mesenchymal stem cells in vitro. Colloids and Surfaces B: Biointerfaces, 135, 386-393. doi:10.1016/j.colsurfb.2015.07.057Chen, Y., Zheng, X., Xie, Y., Ji, H., Ding, C., Li, H., & Dai, K. (2010). Silver release from silver-containing hydroxyapatite coatings. Surface and Coatings Technology, 205(7), 1892-1896. doi:10.1016/j.surfcoat.2010.08.073Actis, L., Gaviria, L., Guda, T., & Ong, J. L. (2013). Antimicrobial surfaces for craniofacial implants: state of the art. Journal of the Korean Association of Oral and Maxillofacial Surgeons, 39(2), 43. doi:10.5125/jkaoms.2013.39.2.43Parvizi, J., Aggarwal, V., & Rasouli, M. (2013). Periprosthetic joint infection: Current concept. Indian Journal of Orthopaedics, 47(1), 10. doi:10.4103/0019-5413.106884Redey, S. A., Nardin, M., Bernache-Assolant, D., Rey, C., Delannoy, P., Sedel, L., & Marie, P. J. (2000). Behavior of human osteoblastic cells on stoichiometric hydroxyapatite and type A carbonate apatite: Role of surface energy. Journal of Biomedical Materials Research, 50(3), 353-364. doi:10.1002/(sici)1097-4636(20000605)50:33.0.co;2-cSpriano, S., Bosetti, M., Bronzoni, M., Vernè, E., Maina, G., Bergo, V., & Cannas, M. (2005). Surface properties and cell response of low metal ion release Ti-6Al-7Nb alloy after multi-step chemical and thermal treatments. Biomaterials, 26(11), 1219-1229. doi:10.1016/j.biomaterials.2004.04.026Vogler, E. A. (1999). Water and the acute biological response to surfaces. Journal of Biomaterials Science, Polymer Edition, 10(10), 1015-1045. doi:10.1163/156856299x00667Lim, J. Y., Liu, X., Vogler, E. A., & Donahue, H. J. (2004). Systematic variation in osteoblast adhesion and phenotype with substratum surface characteristics. Journal of Biomedical Materials Research, 68A(3), 504-512. doi:10.1002/jbm.a.20087Sengstock, C., Diendorf, J., Epple, M., Schildhauer, T. A., & Köller, M. (2014). Effect of silver nanoparticles on human mesenchymal stem cell differentiation. Beilstein Journal of Nanotechnology, 5, 2058-2069. doi:10.3762/bjnano.5.214Sahuquillo Arce, J. M., Iranzo Tatay, A., Llácer Luna, M., Sanchis Boix, Y., Guitán Deltell, J., González Barberá, E., … Gobernado Serrano, M. (2011). Estudio in vitro de las propiedades antimicrobianas de una espuma de poliuretano que libera iones de plata. Cirugía Española, 89(8), 532-538. doi:10.1016/j.ciresp.2011.02.015Jamuna-Thevi, K., Bakar, S. A., Ibrahim, S., Shahab, N., & Toff, M. R. M. (2011). Quantification of silver ion release, in vitro cytotoxicity and antibacterial properties of nanostuctured Ag doped TiO2 coatings on stainless steel deposited by RF magnetron sputtering. Vacuum, 86(3), 235-241. doi:10.1016/j.vacuum.2011.06.011Chernousova, S., & Epple, M. (2012). Silver as Antibacterial Agent: Ion, Nanoparticle, and Metal. Angewandte Chemie International Edition, 52(6), 1636-1653. doi:10.1002/anie.20120592

Expression of ABCA4 in the retinal pigment epithelium and its implications for Stargardt macular degeneration.

Recessive Stargardt disease (STGD1) is an inherited blinding disorder caused by mutations in the Abca4 gene. ABCA4 is a flippase in photoreceptor outer segments (OS) that translocates retinaldehyde conjugated to phosphatidylethanolamine across OS disc membranes. Loss of ABCA4 in Abca4 -/- mice and STGD1 patients causes buildup of lipofuscin in the retinal pigment epithelium (RPE) and degeneration of photoreceptors, leading to blindness. No effective treatment currently exists for STGD1. Here we show by several approaches that ABCA4 is additionally expressed in RPE cells. (i) By in situ hybridization analysis and by RNA-sequencing analysis, we show the Abca4 mRNA is expressed in human and mouse RPE cells. (ii) By quantitative immunoblotting, we show that the level of ABCA4 protein in homogenates of wild-type mouse RPE is about 1% of the level in neural retina homogenates. (iii) ABCA4 immunofluorescence is present in RPE cells of wild-type and Mertk -/- but not Abca4 -/- mouse retina sections, where it colocalizes with endolysosomal proteins. To elucidate the role of ABCA4 in RPE cells, we generated a line of genetically modified mice that express ABCA4 in RPE cells but not in photoreceptors. Mice from this line on the Abca4 -/- background showed partial rescue of photoreceptor degeneration and decreased lipofuscin accumulation compared with nontransgenic Abca4 -/- mice. We propose that ABCA4 functions to recycle retinaldehyde released during proteolysis of rhodopsin in RPE endolysosomes following daily phagocytosis of distal photoreceptor OS. ABCA4 deficiency in the RPE may play a role in the pathogenesis of STGD1

Remarcs on the shape transition from spherical to deformed gamma unstable nuclei

Energies and transition probabilities for low lying states in $^{134}$Ba and ^{104Ru were calculated within a hybrid model.The ground and the first $2^+$ states are described alternatively as a harmonic and anharmonic vibrator states while the remaining states as states with E(5) symmetry. One concludes that a gradual setting of the 'critical' potential yields a better agreement with the experimental data. Very good agreement with the data is obtained for $^{104}$Ru. Comparing the present results with those of E(5) symmetry, it is conspicuous that the present formalism add corrections to the E(5) formalism by bringing the predictions closer to the experimental data. Analytical relationship between the states with U(5) symmetry and those given by the E(5) description is established.Comment: 21 pages, 3 figures, submitted for publicatio

Deformed Harmonic Oscillators for Metal Clusters: Analytic Properties and Supershells

The analytic properties of Nilsson's Modified Oscillator (MO), which was first introduced in nuclear structure, and of the recently introduced, based on quantum algebraic techniques, 3-dimensional q-deformed harmonic oscillator (3-dim q-HO) with Uq(3) > SOq(3) symmetry, which is known to reproduce correctly in terms of only one parameter the magic numbers of alkali clusters up to 1500 (the expected limit of validity for theories based on the filling of electronic shells), are considered. Exact expressions for the total energy of closed shells are determined and compared among them. Furthermore, the systematics of the appearance of supershells in the spectra of the two oscillators is considered, showing that the 3-dim q-HO correctly predicts the first supershell closure in alkali clusters without use of any extra parameter.Comment: 25 pages LaTeX plus 21 postscript figure