Estudios sobre la transcripción en cromosomas politénicos de Chironomus

Los resultados que han dado lugar a esta Tesis pueden agruparse en dos grandes apartados: uno de carácter metodológico, consistente en la puesta a punto de las técnicas bioquímicas aptas para el análisis de la actividad de transcripción en glándulas salivales de Chironomus; otro de carácter temático, donde se estudia la respuesta de la actividad de transcripción a la inhibición de síntesis de proteínas. 1. En primer lugar se han caracterizado las condiciones de marcado radiactivo del RNA, especialmente bajo incubación in vitro de las glándulas aisladas, así como las condiciones de extracción enzimática y posterior purificación del extracto que proporcionan una solución de elevada pureza en ácidos nucleicos. Se ha elaborado también un método de análisis electroforético del RNA glandular, mediante geles de azarosa en columna, caracterizándose de este modo los perfiles de RNA recién sintetizado y estable en Chironomus pallidivittatus y Chironomus thummi. De especia interés, por su total novedad en este sistema biológico, ha sido la puesta a punto de un método que nos permite estimar la tasa de captación (uptake) de uridina-H³, medida como radioactividad ácido-soluble, en glándulas salivales. Su uso nos ha permitido:- Observar que la tasa de captación de uridina es diferencialmente modificada por aplicación in vitro de diversos inhibidores. Comprobar que la discrepancia observada entre el tamaño e intensidad de marcado autorradiográfico en algún puff particular, como consecuencia de un choque térmico, es explicable por los cambios inducidos en la tasa de captación de uridina por efecto del tratamiento.Estas observaciones nos han llevado, para una estimación relativa de la actividad de transcripción, a la necesidad de elaborar factores de corrección que eliminen el influjo de posibles cambios en la tasa de captación del nucleósido precursor. Su aplicación puede modificar cuantitativa, o incluso cualitativamente, las conclusiones inicialmente alcanzadas de la sola consideración de la radiactividad incorporada en RNA.2. En el aspecto temático se ha observado que la aplicación de cicloheximida o anisomicina, a dosis fuertemente inhibitorias de la síntesis de proteínas, inducen un incremento de la radioactividad incorporada en RNA. Dicho incremento no es expicable ni por una modificación en la estabilidad del RNA recién sintetizado ni, al menos totalmente, por el aumento producido en la tasa de captación de uridina-H³. Ello parece indicar que en tales condiciones se induce una activación de la síntesis del RNA. La medida de la actividad RNA polimerasa en células fijadas ha confirmado, de un modo directo, la existencia de dicho aumento de la actividad de transcripción, y que éste es debido, al menos en parte, a una mayor actividad de "iniciación". Por último, el análisis electroforético ha demostrado que la respuesta a la inhibición de la síntesis de proteínas es diferente para las distintas especies de RNA recién sintetizado: Se produce un incremento máximo para el RNA de pequeño tamaño (4-5S). En menor medida, dicho incremento afecta también al hnRNA de grande y mediano peso molecular. La respuesta del RNA de origen nucleolar (pre-rRNA) es distinta según los inhibidores sean aplicados in vitro (produciéndose activación) o in vivo (produciéndose entonces una inhibición selectiva de esta especie de RNA). Estos datos, y otras evidencias morfológicas aducidas, sugieren la existencia de distintos mecanismo de regulación de la transcripción en células politenizadas, con alta especificidad local de acción. Estos mecanismos son discutidos a la luz del fenómeno de "control estricto", y su observación en organismos eucarióticos

Grados de iconicidad y retórica de la imagen

La presente investigación fue motivada por la evidencia rotunda de dificultades en la articulación de conocimientos concernientes al funcionamiento de la imagen como modo comunicacional, observadas en los talleres específicos de la Facultad de Bellas Artes, UNLP. Si el actual desarrollo de las tecnologías de la imagen y de la producción estética se erigen en uno de los patrones básicos de nuestro contacto con lo real, resulta necesario un intento de superación de esas dificultades que se presentan en distintos niveles y ámbitos. La ampliación del dominio de las imágenes solicita de un sistema conceptual apto para su interpretación y transmisión de sentido más allá de las lecturas individuales o los grandes sistemas universalistas de interpretación (las lecturas simbólicas, por ejemplo el psicoanálisis), y para construirlo es necesario reconocer los diversos órdenes de factores que constituyen los frenos que hasta hoy dificultaron la enseñanza de lo visual en un grado de amplitud tal que permitiera analizar imágenes correspondientes a cualquiera de los estatutos que estas adquieren (imperativo-estético-expresivo-etc.).Facultad de Bellas Arte

Grados de iconicidad y retórica de la imagen

La presente investigación fue motivada por la evidencia rotunda de dificultades en la articulación de conocimientos concernientes al funcionamiento de la imagen como modo comunicacional, observadas en los talleres específicos de la Facultad de Bellas Artes, UNLP. Si el actual desarrollo de las tecnologías de la imagen y de la producción estética se erigen en uno de los patrones básicos de nuestro contacto con lo real, resulta necesario un intento de superación de esas dificultades que se presentan en distintos niveles y ámbitos. La ampliación del dominio de las imágenes solicita de un sistema conceptual apto para su interpretación y transmisión de sentido más allá de las lecturas individuales o los grandes sistemas universalistas de interpretación (las lecturas simbólicas, por ejemplo el psicoanálisis), y para construirlo es necesario reconocer los diversos órdenes de factores que constituyen los frenos que hasta hoy dificultaron la enseñanza de lo visual en un grado de amplitud tal que permitiera analizar imágenes correspondientes a cualquiera de los estatutos que estas adquieren (imperativo-estético-expresivo-etc.).Facultad de Bellas Arte

Grados de iconicidad y retórica de la imagen

La presente investigación fue motivada por la evidencia rotunda de dificultades en la articulación de conocimientos concernientes al funcionamiento de la imagen como modo comunicacional, observadas en los talleres específicos de la Facultad de Bellas Artes, UNLP. Si el actual desarrollo de las tecnologías de la imagen y de la producción estética se erigen en uno de los patrones básicos de nuestro contacto con lo real, resulta necesario un intento de superación de esas dificultades que se presentan en distintos niveles y ámbitos. La ampliación del dominio de las imágenes solicita de un sistema conceptual apto para su interpretación y transmisión de sentido más allá de las lecturas individuales o los grandes sistemas universalistas de interpretación (las lecturas simbólicas, por ejemplo el psicoanálisis), y para construirlo es necesario reconocer los diversos órdenes de factores que constituyen los frenos que hasta hoy dificultaron la enseñanza de lo visual en un grado de amplitud tal que permitiera analizar imágenes correspondientes a cualquiera de los estatutos que estas adquieren (imperativo-estético-expresivo-etc.).Facultad de Bellas Arte

Planck early results. XV. Spectral energy distributions and radio continuum spectra of northern extragalactic radio sources

Spectral energy distributions (SEDs) and radio continuum spectra are presented for a northern sample of 104 extragalactic radio sources, based on the Planck Early Release Compact Source Catalogue (ERCSC) and simultaneous multifrequency data. The nine Planck frequencies, from 30 to 857 GHz, are complemented by a set of simultaneous observations ranging from radio to gamma-rays. This is the first extensive frequency coverage in the radio and millimetre domains for an essentially complete sample of extragalactic radio sources, and it shows how the individual shocks, each in their own phase of development, shape the radio spectra as they move in the relativistic jet. The SEDs presented in this paper were fitted with second and third degree polynomials to estimate the frequencies of the synchrotron and inverse Compton (IC) peaks, and the spectral indices of low and high frequency radio data, including the Planck ERCSC data, were calculated. SED modelling methods are discussed, with an emphasis on proper, physical modelling of the synchrotron bump using multiple components. Planck ERCSC data also suggest that the original accelerated electron energy spectrum could be much harder than commonly thought, with power-law indexaround 1.5 instead of the canonical 2.5. The implications of this are discussed for the acceleration mechanisms effective in blazar shocks. Furthermore in many cases the Planck data indicate that gamma-ray emission must originate in the same shocks that produce the radio emission.The Planck Collaboration acknowledges the support of: ESA; CNES and CNRS/INSU-IN2P3-INP (France); ASI, CNR, and INAF (Italy); NASA and DoE (USA); STFC and UKSA (UK); CSIC, MICINN and JA (Spain); Tekes, AoF and CSC (Finland); DLR and MPG (Germany); CSA (Canada); DTU Space (Denmark); SER/SSO (Switzerland); RCN (Norway); SFI (Ireland); FCT/MCTES (Portugal); and DEISA (EU). A description of the Planck Collaboration and a list of its members, indicating which technical or scientific activities they have been involved in, can be found via http://www.rssd.esa.int/Planck. The Metsähovi and Tuorla observing projects are supported by the Academy of Finland (grant numbers 212656, 210338, 121148, 127740 and 122352). UMRAO is supported by a series of grants from the NSF and NASA, and by the University of Michigan. This publication is partly based on data acquired with the Atacama Pathfinder Experiment (APEX). APEX is a collaboration between the Max-Planck-Institut für Radioastronomie, the European Southern Observatory, and the Onsala Space Observatory. This research is partly based on observations with the 100-m telescope of the MPIfR (Max-Planck-Institut für Radioastronomie) at Effelsberg, the IRAM 30-m telescope, and the Medicina (Noto) telescope operated by INAF – Istituto di Radioastronomia. This paper makes use of observations obtained at the Very Large Array (VLA) which is an instrument of the National Radio Astronomy Observatory (NRAO). The NRAO is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. The observations at Xinglong station are supported by the Chinese National Natural Science Foundation grants 10633020, 10778714, and 11073032, and by the National Basic Research Program of China (973 Program) No. 2007CB815403. The OVRO 40-m monitoring program is supported in part by NASA. The Australia Telescope is funded by the Commonwealth of Australia for operation as a National Facility managed by CSIRO. The Fermi LAT Collaboration acknowledges generous ongoing support from a number of agencies and institutes that have supported both the development and the operation of the LAT as well as scientific data analysis. These include the National Aeronautics and Space Administration and the Department of Energy in the United States, the Commissariat à l’Energie Atomique and the Centre National de la Recherche Scientifique/Institut National de Physique Nucléaire et de Physique des Particules in France, the Agenzia Spaziale Italiana and the Istituto Nazionale di Fisica Nucleare in Italy, the Ministry of Education, Culture, Sports, Science and Technology (MEXT), High Energy Accelerator Research Organization (KEK) and Japan Aerospace Exploration Agency (JAXA) in Japan, and the K. A. Wallenberg Foundation, the Swedish Research Council and the Swedish National Space Board in Sweden. Additional support for science analysis during the operations phase is gratefully acknowledged from the Istituto Nazionale di Astrofisica in Italy and the Centre National d’Études Spatiales in France. Part of this work is based on archival data, software or on-line services provided by the ASI Science Data Center ASDC. We thank the Fermi LAT team reviewers, S. Ciprini and M. Giroletti, for their effort and valuable comments

Etoposide-induced differentiation of U937 promonocytic cells: AP-1- dependent gene expression and protein kinase C activation

7 p.-7fig.-1tab. - Pérez et al., 1994The administration of 150 nM etoposide, an inhibitor of DNA topoisomerase II activity, decreased the proliferation and induced the differentiation of U937 human promonocytic cells, as determined by nitroblue tetrazolium reduction, surface accumulation of CD11b/CD18 and CD11c/CD18 integrins, and c-fms protooncogene expression. The expression of these differentiation markers started to be detected at 24 h of treatment. Etoposide caused little cell damage, as determined by trypan blue exclusion and by apoptotic-like DNA degradation, which was slightly initiated at 48 h. The treatment induced a transient increase in c-fos, c-jun, and jun B mRNA levels, with maximum values at 12 h, a transient increase in collagenase mRNA level, with maximum value at 48 h, and a progressive increase in vimentin and lamin A and C mRNAs. These changes were qualitatively similar to those produced by 12-O- tetradecanoylphorbol-13-acetate. Etoposide also caused a transient increase of total AP-1 binding activity, with maximum value at 12 h of treatment, as determined by gel retardation assays. The drug produced an early transient activation (3-6 h) of membrane-bound protein kinase C, followed by the later activation (48 h) of both the membrane and cytosolic enzyme. The protein kinase C inhibitors, sphinganine and 1-(5-isoquinolinylsulfonyl)-2- methylpiperazine (H7), attenuated the induction of differentiation markers by etoposide. These results suggest that protein kinase C and AP-1-dependent gene expression could be involved in myeloid cell differentiation by DNA topoisomerase II inhibitors.Peer reviewe

Quercetin decreases intracellular GSH content and potentiates the apoptotic action of the antileukemic drug arsenic trioxide in human leukemia cells

12 páginas, 7 figuras -- PAGS nros. 1912-1923Arsenic trioxide (ATO) is an effective therapeutic agent for the treatment of acute promyelocytic leukemia, but successful application of this agent may occasionally require the use of sensitizing strategies. The present work demonstrates that the flavonoids quercetin and chrysin cooperate with ATO to induce apoptosis in U937 promonocytes and other human leukemia cell lines (THP-1, HL-60). Co-treatment with ATO plus quercetin caused mitochondrial transmembrane potential dissipation, stimulated the mitochondrial apoptotic pathway, as indicated by cytochrome c and Omi/Htra2 release, XIAP and Bcl-XL down-regulation, and Bax activation, and caused caspase-8/Bid activation. Bcl-2 over-expression abrogated cytochrome c release and apoptosis, and also blocked caspase-8 activation. Quercetin and chrysin, alone or with ATO, decreased Akt phosphorylation as well as intracellular GSH content. GSH depletion was regulated at the level of l-buthionine-(S,R)-sulfoximine (BSO)-sensitive enzyme activity, and N-acetyl-l-cysteine failed both to restore GSH content and to prevent apoptosis. Treatment with BSO caused GSH depletion and potentiated ATO-provoked apoptosis, but did not affect apoptosis induction by ara-C and cisplatin. As an exception, ATO plus quercetin failed to elicit Akt de-phosphorylation and GSH depletion in NB4 acute promyelocytic leukemia cells, and correspondingly exhibited low cooperative effect in inducing apoptosis in this cell line. It is concluded that GSH depletion explains at least in part the selective potentiation of ATO toxicity by quercetin, and that this flavonoid might be used to increase the clinical efficacy of the antileukemic drugThis work was supported by grant SAF2004-01250 from the Plan Nacional de Investigación Científica, Desarrollo e Innovación Tecnológica, Ministerio de Educación y Ciencia, Spain, and HG2005-0036 Spain (MEC)/Greece interchange agreementPeer reviewe

Pharmacologic inhibitors of PI3K/Akt potentiate the apoptotic action of the antileukemic drug arsenic trioxide via glutathione depletion and increased peroxide accumulation in myeloid leukemia cells

7 Figures. 1 Table. The publication costs of this article were defrayed in part by page charge payment. Therefore, and solely to indicate this fact, this article is hereby marked ‘‘advertisement’’ in accordance with 18 U.S.C. section 1734.Treatment for 14 to 24 hours with low concentrations of arsenic trioxide (As2O3, 1-4 µM) caused apoptosis in U-937 promonocytes and other human myeloid leukemia cell lines (HL-60, NB4). This effect was potentiated by cotreatment with the phosphatidylinositol 3-kinase (PI3K) inhibitors LY294002 and wortmannin, and the Akt inhibitor Akti5. However, the inhibitors did not increase the toxicity of the mitochondria-targeting drug lonidamine, and the DNA-specific drugs camptothecin and cisplatin, when used under similar experimental conditions as As2O3. The potentiation of As2O3-provoked apoptosis involved the increased disruption of mitochondrial transmembrane potential, increased caspase-3 activation and cytochrome c release from mitochondria, increased Bax and Bid activation, and attenuation of 27-kDa heat shock protein (HSP27) expression; the potentiation was prevented by Bcl-2 overexpression. The PI3K/Akt inhibitors decreased the intracellular glutathione content, and caused intracellular oxidation, as measured by peroxide accumulation. Cotreatment with subcytotoxic concentrations of hydrogen peroxide increased apoptosis induction by As2O3. On the other hand, the treatments did not significantly affect glutathione S-transferase π expression and activity. These results, which indicate that glutathione is a target of PI3K/Akt in myeloid leukemia cells, may partially explain the selective increase of As2O3 toxicity by PI3K/Akt inhibitors, and may provide a rationale to improve the efficacy of these inhibitors as therapeutic agents.From the Centro de Investigacione Biológicas, Consejo Superior de Investigaciones Científicas, Madrid, Spain. Supported by grant SAF2004-01250 from the Plan Nacional de Investigación Científica, Desarrollo e Innovación Tecnológica, Dirección General de Investigación, Ministerio de Educación y Ciencia, Spain; grant GR/SAL/0639/2004 from the Dirección General de Universidades e Investigación, Consejería de Educación, Comunidad de Madrid, Spain; and by grant 2001-592 from the INTAS program (European Union). A.M.R. was a recipient of a postdoctoral fellowship from the Fundación Carolina, Spain. P.S. and C.F. were recipients of predoctoral fellowships from the Ministerio de Educación, Cultura y Deporte and the Ministerio de Ciencia y Tecnología, Spain, respectively. We thank Dr J. Bre´ard for providing Bcl-2–transfected U-937 cells.Peer reviewe

Application of flow injection analysis to determine protein-bound nitrite in meat products

The development and application of a methodology based on flow injection analysis (FIA) for the determination of protein-bound nitrite (PBN) in meat products was studied. Since the FIA methodology used for measuring residual nitrite was not appropriate for determining PBN (even at a concentration of 15.9 mg of PBN/kg) in meat products, the procedure was modified and then studied for residual nitrites and PBN. Ammonium chloride (A), which is used conventionally (the original FIA method), was replaced by different carriers (the modified FIA method): B (buffer 7); C (buffer 7.5); D (buffer 8); E (NaOH 0.5 M) and F (NaOH 1 M). Carriers B and C provided the lowest limits of quantification of residual nitrite, lower than that obtained using the original FIA method. The method for determining PBN in several meat products (frankfurter and dry sausages) was validated by comparing it with the method usually used. The results obtained indicate that the modified FIA method (with carriers B and C) can be used as a simple, easy, fast, accurate and precise methodology for quantifying residual nitrite and PBN in meat products. © 2005 Elsevier Ltd. All rights reserved.Peer Reviewe

Etoposide stimulates 1,25-dihydroxyvitamin D3 differentiation activity, hormone binding and hormone receptor expression in HL-60 promyelocytic cells

6 páginas, 5 figuras -- PAGS nros. 157-162The simultaneous administration of the DNA topoisomerase II inhibitor etoposide (0.15 mM) and 1,25-dihydroxyvitamin D3 (VD3) (10 nM) synergistically induced the differentiation of HL-60 human promyelocytic leukemia cells. Similar results were obtained using U-937 human promonocytic cells, or the topoisomerase II inhibitors doxorubicin (15 nM) and mitoxantrone (2.5 nM). When sequential treatments were used, pre-incubation with VD3 had little effect on the subsequent action of etoposide, while pre-incubation with etoposide greatly potentiated the subsequent action of VD3. In addition, etoposide treatment stimulated VD3 binding activity and increased VD3 receptor mRNA and protein levels. The increase in hormone receptor expression may explain, at least in part, the capacity of topoisomerase inhibitors to potentiate the differentiation inducing activity of VD3This work was supported by Grant PB94-0063 from the Dirección General de Investigación Científica y Técnica (Spain), Grant 08.1/0027/1997 from the Comunidad Autónoma de Madrid (Spain), and Grant PB96-0373 from the Dirección General de Enseñanza Superior (Spain)Peer reviewe