Análise do efeito de nanopartículas de prata contra células aderidas e biofilmes de Candida albicans e Candida glabrata

O aumento na resistência dos biofilmes de Candida à terapia antifúngica convencional tem despertado o interesse no uso da prata como um agente antimicrobiano. Assim, o objetivo deste trabalho foi avaliar a eficácia antifúngica de nanopartículas de prata (NPs) contra células aderidas e biofilmes de Candida albicans e Candida glabrata. Métodos: NPs esféricas (5 nm) foram sintetizadas através da redução do nitrato de prata pelo citrato de sódio. Testes de mínima concentração inibitória (MCI) foram realizados para as duas espécies de Candida de acordo com o método da microdiluição. NPs foram aplicadas sobre células aderidas (2 hrs) e biofilmes (48 hrs), e após 24 horas de contato os biofilmes resultantes foram caracterizados através da contagem do número de unidades formadoras de colônias (UFCs) e quantificação da biomassa total. Resultados: Os valores de MCI para C. glabrata foram maiores (0,4 – 3,3 µg/mL) do que para C. albicans (0,4 – 1,6 µg/mL). NPs foram mais efetivas na redução da biomassa total quando aplicadas sobre células aderidas do que sobre biofilmes pré-formados. NPs também foram altamente efetivas na redução das UFCs quando aplicadas sobre as células aderidas de C. glabrata (~70%) e respectivos biofilmes (~50%). Para as cepas de C. albicans o efeito não foi tão notório, mas também existiu uma redução no número de UFCs. Conclusão: NPs apresentam potencial como agente antifúngico alternativo no controle de infecções por espécies de Candida

Avaliação da capacidade de adesão de células de biofilmes de Candida após tratamento com nanopartículas de prata

O objetivo deste estudo foi investigar a capacidade de adesão a células epiteliais humanas e a superfície de poliestireno de leveduras viáveis recuperadas de biofilmes de Candida albicans e Candida glabrata tratados com nanopartículas de prata (NP). Métodos: Biofilmes de Candida (48 hrs) foram formados em placas de microtitulação de 6 poços e tratados por 24 horas com NP (5 nm) nas concentrações de 13,5 e 54 mg/L. Suspensões de células de Candida (107 células viáveis/mL em RPMI 1640) provenientes dos biofilmes tratados com NP foram adicionadas a monocamadas de células HeLa e a poços vazios de placas de microtitulação de 24 poços (para estudar adesão a poliestireno). Após 2 horas de contato, a adesão das leveduras foi determinada usando a coloração com violeta cristal. Resultados: A capacidade de adesão de leveduras viáveis a células HeLa e a superfícies de poliestireno foi significativamente reduzida, e esta redução foi maior quando os biofilmes foram pré-tratados com NP na concentração de 54 mg/L. Ainda, a quantidade de leveduras aderidas das duas cepas diferiu de acordo com o substrato (células epiteliais e superfície de poliestireno). Conclusão: NP podem induzir modificações em leveduras viáveis, as quais podem diminuir a disseminação de infecções por Candida, principalmente em pacientes imunocomprometidos

Nearly optimal solutions for the Chow Parameters Problem and low-weight approximation of halfspaces

The \emph{Chow parameters} of a Boolean function $f: \{-1,1\}^n \to \{-1,1\}$ are its $n+1$ degree-0 and degree-1 Fourier coefficients. It has been known since 1961 (Chow, Tannenbaum) that the (exact values of the) Chow parameters of any linear threshold function $f$ uniquely specify $f$ within the space of all Boolean functions, but until recently (O'Donnell and Servedio) nothing was known about efficient algorithms for \emph{reconstructing} $f$ (exactly or approximately) from exact or approximate values of its Chow parameters. We refer to this reconstruction problem as the \emph{Chow Parameters Problem.} Our main result is a new algorithm for the Chow Parameters Problem which, given (sufficiently accurate approximations to) the Chow parameters of any linear threshold function $f$, runs in time \tilde{O}(n^2)\cdot (1/\eps)^{O(\log^2(1/\eps))} and with high probability outputs a representation of an LTF $f'$ that is \eps-close to $f$. The only previous algorithm (O'Donnell and Servedio) had running time \poly(n) \cdot 2^{2^{\tilde{O}(1/\eps^2)}}. As a byproduct of our approach, we show that for any linear threshold function $f$ over $\{-1,1\}^n$, there is a linear threshold function $f'$ which is \eps-close to $f$ and has all weights that are integers at most \sqrt{n} \cdot (1/\eps)^{O(\log^2(1/\eps))}. This significantly improves the best previous result of Diakonikolas and Servedio which gave a \poly(n) \cdot 2^{\tilde{O}(1/\eps^{2/3})} weight bound, and is close to the known lower bound of $\max\{\sqrt{n},$ (1/\eps)^{\Omega(\log \log (1/\eps))}\} (Goldberg, Servedio). Our techniques also yield improved algorithms for related problems in learning theory

Nanopartículas de prata : análise dos efeitos anti-biofilme e anti-adesão sobre Candida albicans e Candida glabrata

Os objetivos deste trabalho foram: (1) avaliar o efeito sinergístico de nanopartículas de prata (NP) com Nistatina e Clorexidina contra biofilmes de Candida albicans e Candida glabrata; (2) verificar o efeito das NP na composição da matriz destes biofilmes e (3) investigar a capacidade de adesão a células epiteliais HeLa e a poliestireno de leveduras tratadas com NP. As drogas sozinhas ou em combinação com NP (5 nm) foram aplicadas sobre biofilmes maduros (48 h) e após 24 h de contato a atividade sinergística foi avaliada através da quantificação da biomassa total e por meio da contagem do número de colônias. Após o tratamento com NP, as matrizes dos biofilmes foram extraídas e analisadas em termos de proteínas, carboidratos e DNA. Ainda, leveduras viáveis foram recuperadas e adicionadas tanto às células HeLa quanto aos poços vazios de placas de poliestireno e, após 2 horas de contato, a adesão foi determinada usando violeta cristal. NP combinadas com Nistatina e Clorexidina exibiram atividade anti-biofilme sinergística dependente das espécies e concentrações de drogas usadas. Ainda, NP interferiram na composição da matriz extracelular dos biofilmes e a capacidade de adesão das leveduras viáveis foi significativamente reduzida após tratamento prévio com NP. Esses achados permitem concluir que NP podem contribuir na prevenção ou tratamento da estomatite protética associada à Candida. Entretanto, estudos adicionais são necessários para que estas NP sejam usadas com segurança

The DEEP Groth Strip Galaxy Redshift Survey. III. Redshift Catalog and Properties of Galaxies

The Deep Extragalactic Evolutionary Probe (DEEP) is a series of spectroscopic surveys of faint galaxies, targeted at the properties and clustering of galaxies at redshifts z ~ 1. We present the redshift catalog of the DEEP 1 GSS pilot phase of this project, a Keck/LRIS survey in the HST/WFPC2 Groth Survey Strip. The redshift catalog and data, including reduced spectra, are publicly available through a Web-accessible database. The catalog contains 658 secure galaxy redshifts with a median z=0.65, and shows large-scale structure walls to z = 1. We find a bimodal distribution in the galaxy color-magnitude diagram which persists to z = 1. A similar color division has been seen locally by the SDSS and to z ~ 1 by COMBO-17. For red galaxies, we find a reddening of only 0.11 mag from z ~ 0.8 to now, about half the color evolution measured by COMBO-17. We measure structural properties of the galaxies from the HST imaging, and find that the color division corresponds generally to a structural division. Most red galaxies, ~ 75%, are centrally concentrated, with a red bulge or spheroid, while blue galaxies usually have exponential profiles. However, there are two subclasses of red galaxies that are not bulge-dominated: edge-on disks and a second category which we term diffuse red galaxies (DIFRGs). The distant edge-on disks are similar in appearance and frequency to those at low redshift, but analogs of DIFRGs are rare among local red galaxies. DIFRGs have significant emission lines, indicating that they are reddened mainly by dust rather than age. The DIFRGs in our sample are all at z>0.64, suggesting that DIFRGs are more prevalent at high redshifts; they may be related to the dusty or irregular extremely red objects (EROs) beyond z>1.2 that have been found in deep K-selected surveys. (abridged)Comment: ApJ in press. 24 pages, 17 figures (12 color). The DEEP public database is available at http://saci.ucolick.org

Palomar 13's Last Stand

We present a proper motion and CCD photometric study of stars in the distant halo globular cluster Palomar 13. The absolute proper motion of Pal 13 with respect to the background galaxies, derived from moderate scale photographic plates separated by a 40-year baseline, is $(\mu_{\alpha cos \delta}, \mu_{\delta}) = (+2.30, +0.27) \pm (0.26, 0.25)$ milliarc-seconds per year. The resultant total space velocity (315 km s$^{-1}$) implies that Pal 13 is in the inner part of its orbit near perigalacticon. Orbital integration reveals the cluster to possess an inclined, very eccentric, retrograde orbit. These data confirm that Pal 13 is a paradigm "young halo" globular cluster. The derived proper motions for cluster stars are used to produce membership probabilities and a cleaned CCD UBV catalogue for Pal 13. With this data set we have made small revisions to Pal 13's distance, metallicity, position and light profile. The membership of four previously reported RR Lyrae variables and a proportionally large group of blue straggler stars are confirmed. As expected, the blue stragglers are centrally concentrated. The small size of this cluster, combined with the shape of its light profile, which shows a clear departure from a classical King function beyond the tidal radius, suggests that Pal 13 is in the final throes of destruction. This could explain the large blue straggler specific frequency, as destructive processes would preferentially strip less massive stars.Comment: 54 pages, 9 figures, 7 tables, accapted for publication in February 2001 A

The Galaxy Structure-Redshift Relationship

There exists a gradual, but persistent, evolutionary effect in the galaxy population such that galaxy structure and morphology change with redshift. This galaxy structure-redshift relationship is such that an increasingly large fraction of all bright and massive galaxies at redshifts 2 < z < 3 are morphologically peculiar at wavelengths from rest-frame ultraviolet to rest-frame optical. There are however examples of morphologically selected spirals and ellipticals at all redshifts up to z ~ 3. At lower redshift, the bright galaxy population smoothly transforms into normal ellipticals and spirals. The rate of this transformation strongly depends on redshift, with the swiftest evolution occurring between 1 < z < 2. This review characterizes the galaxy structure-redshift relationship, discusses its various physical causes, and how these are revealing the mechanisms responsible for galaxy formation.Comment: 20 pages, 8 figures. Invited Review to appear in "Penetrating Bars Through Masks of Cosmic Dust: The Hubble Tuning Fork Strikes A New Note", ed. D. Block et a

Yield Measurements for ^7Be and ^<10>Be Productions from ^<nat>Cu, ^<nat>Ag and ^<197>Au by Bremsstrahlung Irradiation at E_0=200 MeV(II. Radiochemistry)

The yields of ^7Be and ^Be produced by bremsstrahlung having a maximum energy (E_0) of 200 MeV in ^Cu, ^Ag and ^Au targets were investigated by the AMS technique at MALT of the University of Tokyo. It was found that the yields at E_0 = 200 MeV were much lower than those at E_0 ≧250 MeV, obtained in our previous work. A change in the yields of the fragmentation component in the target-mass dependence was observed at E_0=200 MeV when compared with those at E_0≧250 MeV. However, the ratios of the fragmentation yield of ^Be to that of ^7Be remained unchanged throughout the concerned E_0

Radial Distribution of the Mass-to-Luminosity Ratio in Spiral Galaxies and Massive Dark Cores

We derive radial profiles of the surface-mass-density for 19 spiral galaxies directly from their high-resolution rotation curves. Using the corresponding luminosity profiles, we obtain the radial distribution of the mass-to-luminosity ratios ($M/L$) from the inner bulge ($\sim$ a few 100 pc) to the outer disk ($\geq$ 2-10 kpc) for 11 galaxies (with inclination < $70^{\circ}$ in order to reduce the influence of the interstellar extinction. The $M/L$s in the bulges of two galaxies with sufficient resolution, NGC 4527 and NGC 6946, are found to increase steeply toward the center at radii $\sim$ 100-500 pc at rates of 15$\pm$3 and 7$\pm$2 times per kpc, respectively. Some other galaxies with fairly high resolution also show signs of an increase toward the center. Such an increase may indicate the existence of a new component, a ``massive dark core'', which may be an object linking the bulge and a central black hole. Based on radial variations of the $M/L$, we further discuss the variation of the dark-mass fraction in spiral galaxies.Comment: Latex 19 pages, 30 ps figures. ApJ in pres

An ensemble-averaged, cell density-based digital model of zebrafish embryo development derived from light-sheet microscopy data with single-cell resolution

A new era in developmental biology has been ushered in by recent advances in the quantitative imaging of all-cell morphogenesis in living organisms. Here we have developed a light-sheet fluorescence microscopy-based framework with single-cell resolution for identification and characterization of subtle phenotypical changes of millimeter-sized organisms. Such a comparative study requires analyses of entire ensembles to be able to distinguish sample-to-sample variations from definitive phenotypical changes. We present a kinetic digital model of zebrafish embryos up to 16h of development. The model is based on the precise overlay and averaging of data taken on multiple individuals and describes the cell density and its migration direction at every point in time. Quantitative metrics for multi-sample comparative studies have been introduced to analyze developmental variations within the ensemble. The digital model may serve as a canvas on which the behavior of cellular subpopulations can be studied. As an example, we have investigated cellular rearrangements during germ layer formation at the onset of gastrulation. A comparison of the one-eyed pinhead (oep) mutant with the digital model of the wild-type embryo reveals its abnormal development at the onset of gastrulation, many hours before changes are obvious to the eye