Search

The limb forms from a bud of mesoderm encased in a hull of ectoderm that grows out from the flank of the embryo. Coordinated signaling between the limb mesoderm and ectoderm is critical for normal limb outgrowth and patterning. The apical ectodermal ridge (AER), found at the distal tip, is a rich source of signaling molecules and has been proposed to specify distal structures and maintain the survival of cells in the underlying distal mesoderm. The dorsal and ventral non-AER ectoderm is also a source of signaling molecules and is important for dorsal-ventral patterning of the limb bud. Here we determine if this ectoderm provides cell survival signals by surgically removing the dorsal or ventral ectoderm during early chicken limb bud development and assaying for programmed cell death. We find that, similar to the AER, removal of the dorsal or ventral non-AER ectoderm results in massive cell death in the underlying mesoderm. In addition, although a re-epithelialization occurs, we find perturbations in the timing of Shh expression and, for the case of the dorsal ectoderm removal, defects in soft tissue and skeletal development along the proximal-distal axis. Furthermore, ectoderm substitution experiments show that the survival signal produced by the dorsal limb ectoderm is specific. Thus, our results argue that the non-AER ectoderm, like the AER, provides a specific survival signal to the underlying mesoderm that is necessary for normal limb development and conclusions drawn from experiments in which the non-AER ectoderm is removed, need to take into consideration this observation. © 2013 Elsevier Inc.

Limb development relies on an exquisite coordination between growth and patterning, but the underlying mechanisms remain elusive. Anterior-posterior and proximal-distal specification initiates in early limb bud concomitantly with the proliferative expansion of limb cells. Previous studies have shown that limb bud growth initially relies on fibroblast growth factors (FGFs) produced in the apical ectodermal ridge (AER-FGFs), the maintenance of which relies on a positive-feedback loop involving sonic hedgehog (Shh) and the BMP antagonist gremlin 1 (Grem1). The positive cross-regulation between Shh and the HoxA and HoxD clustered genes identified an indirect effect of Hox genes on the maintenance of AER-FGFs but the respective function of Shh and Hox genes in this process remains unknown. Here, by uncoupling Hox and Shh function, we show that HoxA and HoxD genes are required for proper AER-FGFs expression, independently of their function in controlling Shh expression. In addition, we provide evidence that the Hoxdependent control of AER-FGF expression is achieved through the regulation of key mesenchymal signals, namely Grem1 and Fgf10, ensuring proper epithelial-mesenchymal interactions. Notably, HoxA and HoxD genes contribute to both the initial activation of Grem1 and the subsequent anterior expansion of its expression domain. We propose that the intricate interactions between Hox genes and the FGF and Shh signaling pathways act as a molecular network that ensures proper limb bud growth and patterning, probably contributing to the coordination of these two processes. © 2013. Published by The Company of Biologists Ltd.

The two enantiomers of the nonsteroidal antiinflammatory drug naproxen and of its methyl ester have been selected as representative probes with markedly different hydrophobicity to assess the potential of cholic acid aggregates as drug carriers by means of photophysical techniques. The different distribution of the probes between bulk solution and aggregates has been assessed by quenching of their singlet and triplet excited states by iodide and nitrite anions, respectively. This straightforward photophysical methodology can, in principle, be extended to a variety of drugs containing a photoactive chromophore. © 2012 American Chemical Society.

En este trabajo se presenta el estudio estratigráfico por microscopía electrónica con sonda de energías dispersivas (SEMEDX) de costras y depósitos superficiales formados en las fachadas de veinticinco templos, del siglo XIII al XIX, del centro histórico y del barrio de Triana en Sevilla. Entre los indicadores de alteración de las fachadas de estos templos se han detectado depósitos superficiales y costras negras sobre la piedra, mortero y ladrillo, que están formados principalmente por yeso (CaSO4.2H2O). Los estudios de azufre por microscopía electrónica (SEM-EDX) se han realizado a lo largo de una línea perpendicular a la superficie. Este análisis combinado con la descripción por microscopio óptico permite calificar las alteraciones superficiales en cuatro grupos: a) costras compuestas por azufre y calcio, las más abundantes; b) muestras con superposición de capas de alteración y reposición; c) costras de origen orgánico (biocostras), que en su composición no contienen azufre; y d) depósitos superficiales en los que no se ha generado ningún tipo de reacción química y están formados fundamentalmente por polvo, terrígenos y otras partículas atmosféricas. Como consecuencia de este estudio, se puede afirmar que las portadas de las iglesias analizadas están sufriendo un deterioro acelerado por la acción de las emisiones generadas por el tráfico rodado. En los centros históricos es, por tanto, aconsejable la realización de estudios y modelos microclimáticos, para establecer perímetros de vulnerabilidad, discriminar factores de riesgo y definir medidas de prevención del estado de conservación de la fábrica exterior del patrimonio arquitectónico.

Generation of triplet eximers of 6-fluoro-7-piperazinylquinolone-3-carboxylic acids (FQs) have been detected in aqueous media using laser flash photolysis (LFP). These transient species (SS) are generated by self-quenching reactions of FQ triplet excited states such as pefloxacin (PFX), norfloxacin (NFX), the N-acetylated form of NFX (ANFX), and its methyl ester (EANFX) with their ground states. In this context, self-quenching rate constants in the range of (1-7) X 10(8) M-1 s(-1) were determined. The triplet excimers show transient absorption spectra with lambda(max) ca. 710 nm for SSNFX, 740 nm for SSPFX, and 620 nm for SSANFX and E-ANFX, which are red-shifted with respect to their predecessors triplet excited states. These excimers can be also observed in the presence of phosphate buffer (PB). Experiments performed with NFX and ANFX at different PB concentrations showed that deprotonation processes are not involved in the generation of SS. The triplet multiplicity of the FQ excimers was confirmed by energy transfer reactions with naproxen. The correlation between fluorescence, intersystem crossing, excimer and photodegradation quantum yields of (A)NFX indicated that FQ self-quenching reactions are mainly a deactivation pathway. On the other hand, generation of FQ radical anions absorbing at lambda(max) ca. 620 nm has been observed by an efficient electron transfer reaction from Tip to NFX, PFX, and ANFX (rate constants ca. 1 X 109 M-1 s(-1)).

The formation of repetitive structures (such as stripes) in nature is often consistent with a reaction-diffusion mechanism, or Turing model, of self-organizing systems. We used mouse genetics to analyze how digit patterning (an iterative digit/nondigit pattern) is generated. We showed that the progressive reduction in Hoxa13 and Hoxd11-Hoxd13 genes (hereafter referred to as distal Hox genes) from the Gli3-null background results in progressively more severe polydactyly, displaying thinner and densely packed digits. Combined with computer modeling, our results argue for a Turing-type mechanism underlying digit patterning, in which the dose of distal Hox genes modulates the digit period or wavelength. The phenotypic similarity with fish-fin endoskeleton patterns suggests that the pentadactyl state has been achieved through modification of an ancestral Turing-type mechanism.

Sirenomelia is a severe congenital malformation of the lower body characterized by the fusion of the legs into a single lower limb. This striking external phenotype consistently associates severe visceral abnormalities, most commonly of the kidneys, intestine, and genitalia that generally make the condition lethal. Although the causes of sirenomelia remain unknown, clinical studies have yielded two major hypotheses: i) a primary defect in the generation of caudal mesoderm, ii) a primary vascular defect that leaves the caudal part of the embryo hypoperfused. Interestingly, Sirenomelia has been shown to have a genetic basis in mice, and although it has been considered a sporadic condition in humans, recently some possible familial cases have been reported. Here, we report that the removal of one or both functional alleles of Shh from the Bmp7-null background leads to a sirenomelia phenotype that faithfully replicates the constellation of external and internal malformations, typical of the human condition. These mutants represent an invaluable model in which we have analyzed the pathogenesis of sirenomelia. We show that the signaling defect predominantly impacts the morphogenesis of the hindgut and the development of the caudal end of the dorsal aortas. The deficient formation of ventral midline structures, including the interlimb mesoderm caudal to the umbilicus, leads to the approximation and merging of the hindlimb fields. Our study provides new insights for the understanding of the mechanisms resulting in caudal body malformations, including sirenomelia. © 2012 Garrido-Allepuz et al.

Cinacalcet (CIN) is a calcimimetic drug, which contains a naphthalene chromophore and binds almost quantitatively to human serum albumin (HSA). In the present work, the excited states of CIN have been characterized in order to obtain relevant information about complexation of CIN with HSA. The fluorescence spectrum in acetonitrile, at lambda(exc) = 290 nm, displayed two bands with maxima at 332 and 439 nm, assigned to the monomer and exciplex emission. Upon protonation of the amino group, the exciplex band disappeared, with a concomitant increase of the monomer emission intensity. Time-resolved fluorescence evidenced an intramolecular dynamic quenching, attributed to exciplex formation and/or photoinduced electron transfer, in agreement with the favorable thermodynamics predicted by the Rehm-Weller equations. Diffusion controlled dynamic quenching of CINH(+) fluorescence by oxygen was observed. The emission properties in PBS were similar to those obtained for CINH(+) in acetonitrile. Laser flash photolysis (LFP) of CIN and CINH(+) in aCetonitrile/N(2), at lambda(exc) = 308 nm, gave rise to the naphthalene-like triplet excited states, with maxima at 420 nm and lifetimes of 4 and 7 mu s; they were efficiently quenched by oxygen. No significant singlet excited state interaction was observed in CINH(+)/HSA complexes, as revealed by the emission spectra, which were roughly explained taking into account the relative contributions of drug and protein in the absorption spectra. Upon LFP of the complexes, triplet excited states were generated; the decays monitored at 420 nm were satisfactorily fitted using a function containing two monoexponential terms, corresponding to a Short-lived (tau(1) = 8 mu s) and a long-lived (tau(2) = 37 mu s) component. This indicates that the drug is incorporated into two different binding sites of HSA. Despite the long triplet lifetimes of the CINH(+)/HSA complexes, the rate constant of quenching by oxygen was found to be 2 orders of magnitude

Background: Hypersensitivity IgE-mediated reactions to quinolones are not easy to diagnose, with skin testing inducing false positive results. The aim of the study was to evaluate the in vitro-specific IgE response in patients with immediate allergic reactions to quinolones. Methods: We evaluated 38 patients with confirmed immediate allergic reactions to quinolones. Those with anaphylaxis were considered allergic by clinical history, once other possible causes were ruled out, and those with urticaria by drug provocation. Sepharose-radioimmunoassay (RIA) and basophil activation test (BAT) with ciprofloxacin, moxifloxacin and levofloxacin were performed. Results: The quinolones involved were moxifloxacin (N = 24), ciprofloxacin (N = 11) and levofloxacin (N = 3). Sepharose-RIA was positive in 12 cases (31.57%) and BAT in 27 (71.05%). With Sepharose-RIA, 8 (21%) were positive to ciprofloxacin, 7 (18.4%) to moxifloxacin and 7 (18.4%) to levofloxacin. With BAT, 23 (60.5%) were positive to ciprofloxacin, 12 (31.6%) to moxifloxacin and 8 (21%) to levofloxacin. The specificity of the Sepharose-RIA was demonstrated by inhibition tests. To confirm that the BAT results observed were IgE mediated, the PI3K inhibitor wortmannin was used, with this compound inhibiting the BAT when stimulated with anti-IgE and the different quinolones, but not when fMLP was used as the basophil stimulator. Sepharose-RIA and BAT were repeated in positive cases 1 year later, detecting a decrease in all cases, with four becoming negative. Conclusion: Immediate hypersensitivity reactions to quinolones do occur, with moxifloxacin being the drug most frequently involved. The BAT is a useful method for diagnosing patients. Specific IgE was demonstrated by Sepharose-RIA and inhibition assay. © 2010 John Wiley & Sons A/S.

[EN] Hydrogen abstraction from the C-7 position of cholesterol (Ch) by triplet excited benzophenone (BZP) exhibits remarkable solvent-dependence in product studies. Kinetic measurements on the intramolecular version of the process in dyads containing covalently linked Ch and BZP units reveal important solvent effects and significant stereodifferentiation.

A thorough mechanistic study has been performed on the reaction between benzophenone (BZP) and a series of 1,4-dienes, including 1,4-cyclohexadiene (CHD), 1,4-dihydro-2-methylbenzoic acid (MBA), 1,4-dihydro-1,2-dimethylbenzoic acid (DMBA) and linoleic acid (LA). A combination of steady-state photolysis, laser flash photolysis (LFP), and photochemically induced dynamic nuclear polarization (photo-CIDNP) have been used. Irradiation of BZP and CHD led to a cross-coupled sensitizer¿diene product, together with 6, 7, and 8. With MBA and DMBA as hydrogen donors, photoproducts arising from cross-coupling of sensitizer and diene radicals were found; compound 7 was also obtained, but 6 and o-toluic acid were only isolated in the irradiation of BZP with MBA. Triplet lifetimes were determined in the absence and in the presence of several diene concentrations. All three model compounds showed similar reactivity (kq¿108¿m¿1¿s¿1) towards triplet excited BZP. Partly reversible hydrogen abstraction of the allylic hydrogen atoms of CHD, MBA, and DMBA was also detected by photo-CIDNP on different timescales. Polarizations of the diamagnetic products were in full agreement with the results derived from LFP. Finally, LA also underwent partly reversible hydrogen abstraction during photoreaction with BZP. Subsequent hydrogen transfer between primary radicals led to conjugated derivatives of LA. The unpaired electron spin population in linoleyl radical (LA.) was predominantly found on H(1-5) protons. To date, LA-related radicals were only reported upon hydrogen transfer from highly substituted model compounds by steady-state EPR spectroscopy. Herein, we have experimentally established the formation of LA. and shown that it converts into two dominating conjugated isomers on the millisecond timescale. Such processes are at the basis of alterations of membrane structures caused by oxidative stress.

[EN] Three drugs containing the naphthalene (NP) chromophore, namely, naproxen (NPX), propranolol (PPN), and cinacalcet (CIN), but with different affinities toward serum albumins (SAs) and alpha-1-acid glycoproteins (AAGs) have been employed for the assessment of drug distribution in binary SA/AAG systems. These three drugs represent an appropriate choice for checking whether a methodology based on transient absorption spectroscopy of a given reporter can be employed for discrimination between different distribution patterns in multicompartmental biological media. Thus, upon laser flash photolysis (LFP) of NPX, PPN, and CIN in the presence or absence of proteins, the NP triplet excited state ((NP)-N-3*) at similar to 420 nm was always detected, although the kinetics of the decay traces was structure- and medium-dependent. In aerated PBS, only a very short triplet lifetime (tau(T)) was found (1-2 mu s). By contrast, in the presence of SAs, two longer triplet lifetimes (5-76 mu s) were observed, ascribed to (NP)-N-3* within site land site II. Upon binding to AAGs, only a long tau(T) (15-47 mu s) was found. When the two proteins were present simultaneously in the same media, fitting of the decay traces was clearly consistent with a distribution of the drug between the different biological compartments and the bulk solution, which correlates well with the known protein affinities of every drug. Experiments were performed in both human (HSA/HAAG) and bovine protein media (BSA/BAAG). The results showed that SAs are the major carriers for NPX; by contrast, PPN binds preferentially to AAGs. An intermediate situation was found for CIN, which presents comparable affinity for both proteins. The results obtained for the two enantiomers of each drug were very similar, although a small stereodifferentiation was observed between the triplet lifetimes in the protein binding sites.

El presente estudio se propone comprender las variables no observables respecto a los sistemas de discriminación en el ámbito empresarial a través de metodologías cualitativas. El ámbito empresarial no representa un espacio social homogéneo. Por el contrario, las empresas tienen diferentes tamaños, estructuras y culturas organizacionales. Es por ello que mediante la revisión de fuentes cuantitativas y entrevistas personales, se aborda la investigación de empresas grandes, medianas y pequeñas según sus propias especificidades, poniendo en evidencia las diferentes formas en que la discriminación se reproduce en ellas. Las maneras de discriminación no se instauran exclusivamente debido a los estereotipos y prejuicios compartidos, sino también debido a las estructuras de las organizaciones. Del mismo modo, los mecanismos de discriminación y su percepción varían con relación al sexo, la edad, la orientación sexual, la raza, el nivel socioeconómico y el tamaño de las empresas.

Two broad classes of models have been proposed to explain the patterning of the proximal-distal axis of the vertebrate limb (from the shoulder to the digit tips). Differentiating between them, we demonstrate that early limb mesenchyme in the chick is initially maintained in a state capable of generating all limb segments through exposure to a combination of proximal and distal signals. As the limb bud grows, the proximal limb is established through continued exposure to flank-derived signal(s), whereas the developmental program determining the medial and distal segments is initiated in domains that grow beyond proximal influence. In addition, the system we have developed, combining in vitro and in vivo culture, opens the door to a new level of analysis of patterning mechanisms in the limb.

Vertebrate limbs develop three main proximodistal (PD) segments (upper arm, forearm, and hand) in a proximal-to-distal sequence. Despite extensive research into limb development, whether PD specification occurs through nonautonomous or autonomous mechanisms is not resolved. Heterotopic transplantation of intact and recombinant chicken limb buds identifies signals in the embryo trunk that proximalize distal limb cells to generate a complete PD axis. In these transplants, retinoic acid induces proximalization, which is counteracted by fibroblast growth factors from the distal limb bud; these related actions suggest that the first limb-bud PD regionalization results from the balance between proximal and distal signals. The plasticity of limb progenitor cell identity in response to diffusible signals provides a unifying view of PD patterning during vertebrate limb development and regeneration.

Sirenomelia, also known as sirenomelia sequence, is a severe malformation of the lower body characterized by fusion of the legs and a variable combination of visceral abnormalities. The causes of this malformation remain unknown, although the discovery that it can have a genetic basis in mice represents an important step towards the understanding of its pathogenesis. Sirenomelia occurs in mice lacking Cyp26a1, an enzyme that degrades retinoic acid (RA), and in mice that develop with reduced bone morphogenetic protein (Bmp) signaling in the caudal embryonic region. The phenotypes of these mutant mice suggest that sirenomelia in humans is associated with an excess of RA signaling and a deficit in Bmp signaling in the caudal body. Clinical studies of sirenomelia have given rise to two main pathogenic hypotheses. The first hypothesis, based on the aberrant abdominal and umbilical vascular pattern of affected individuals, postulates a primary vascular defect that leaves the caudal part of the embryo hypoperfused. The second hypothesis, based on the overall malformation of the caudal body, postulates a primary defect in the generation of the mesoderm. This review gathers experimental and clinical information on sirenomelia together with the necessary background to understand how deviations from normal development of the caudal part of the embryo might lead to this multisystemic malformation.

Varios modelos han sido propuestos para explicar cómo ocurre la especificación proximo-distal durante el desarrollo de la extremidad de los vertebrados. Sin embargo, ninguno de estos modelos es completamente satisfactorio para explicar los resultados de los experimentos y manipulaciones genéticas realizados. Actualmente, uno de los modelos más aceptados es el modelo de la Zona de Progreso. El experimento de irradiación con rayos X de la extremidad del embrión de pollo (Wolpert et al., 1979), ha constituido durante años el apoyo más fuerte a este modelo. Debido a la importancia del experimento y a que cuando fue realizado no se disponía de las técnicas moleculares que tenemos en la actualidad, el objetivo de la presente Tesis Doctoral ha sido hacer una reevaluación de este experimento así como de los modelos existentes. La irradiación de la extremidad del embrión de pollo resulta en extremidades focomélicas. La focomelia es una rara malformación congénita en la que las partes más proximales (las más cercanas al tronco) de las extremidades están reducidas o ausentes. En los casos más severos, las manos o incluso los dedos aparecen directamente unidos al hombro. La incidencia de esta malformación aumentó en los años 60 debido a la prescripción de la talidomida (actualmente un reconocido teratógeno) para aliviar las náuseas del embarazo. Puesto que la talidomida no causa focomelias en el embrión de pollo, esta malformación fue reproducida mediante su irradiación con rayos X en estadíos tempranos. El fenotipo fue interpretado, según el modelo de la Zona de Progreso, como defectos en la especificación de los distintos segmentos esqueléticos y, como ya se ha comentado, ha supuesto durante años un fuerte apoyo a este modelo., En esta tesis, usando una combinación de análisis moleculares y linaje celular, hemos demostrado que la focomelia no está causada por un defecto en la especificación de los distintos segmentos próximo-distales sino por una deficiencia en el proceso de condensación condrogénica de los elementos esqueléticos. Puesto que las condensaciones condrogénicas ocurren en una secuencia proximo-distales, los elementos más proximales se ven afectados cuando la irradiación se realiza en estadíos tempranos del desarrollo, mientras que los más distales se verían afectados si la irradiación se realiza en estadíos más tardíos. Por tanto, nuestros resultados sugieren que el experimento de irradiación de la extremidad del embrión de pollo, no constituye un apoyo al modelo de la Zona de Progreso y demuestran que los fenotipos focomélicos son debidos a interferencias en el proceso de formación de las condensaciones cartilaginosas. Por otro lado, pero relacionado con la especificación del eje próximo-distal, un nuevo mutante condicional de Fgf8, Fgf8;Mox2Cre, fue analizado. En los mutantes Fgf8;Mox2Cre, Fgf8 es inactivado en el epiblasto. Sin embargo, la inactivación es incompleta y quedan algunas células residuales que expresan Fgf8. Nuestro objetivo fue comparar los fenotipos resultantes de esa inactivación incompleta con otros mutantes condicionales de Fgf8 en los que la inactivación es completa o en los que Fgf8 se inactiva después de que la expresión se haya iniciado. La comparación entre los distintos mutantes de Fgf8 es interesante para una mayor comprensión del papel de los FGFs en el desarrollo de la extremidad. De nuestro análisis concluimos que el fenotipo de los mutantes Fgf8;Mox2Cre es similar al de las extremidades anteriores de los mutantes Msx2-Cre;Fgf8, en los que la expresión de Fgf8 se inicia normalmente pero dura un corto periodo de tiempo. Por tanto una pequeña cantidad de Fgf8 pero mantenida, es igual que una corta normal expresión al inicio. Ésta equivalencia funcio

En los vertebrados, el desarrollo de la extremidad comienza cuando las células mesodérmicas indiferenciadas de la capa somática del MPL se acumulan bajo el ectodermo de la pared lateral del cuerpo y la extremidad emerge como una pequeña protuberancia, el esbozo de extremidad, formado por células mesodérmicas recubiertas de una capa ectodérmica. El posterior desarrollo de la extremidad depende de una serie de interacciones recíprocas entre el ectodermo y el mesodermo (E-M) que son cruciales para la morfogénesis del esbozo de extremidad., Este proceso implica la formación de patrón, conjunto de procesos en el que las células indiferenciadas reciben información posicional y son especificadas, determinadas y posteriormente diferenciadas para formar una estructura. Esta información posicional se realiza a través de vías de señalización, mediadas por moléculas señalizadoras, que pueden ser agrupadas en cuatro grandes familias: la familia WNT, la familia de los FGFs, la familia HEDGEHOG y la superfamilia de los TGFs. La transducción de señal por estos ligandos depende de una serie de factores de transcripción, entre los que cabe destacar, por su importancia en el desarrollo de la extremidad, la familia de las proteínas GLI y la familia de las proteínas HOX. Estudios embriológicos clásicos e investigaciones a nivel molecular han permitido identificar varios centros señalizadores u organizadores de la extremidad en desarrollo, que regulan y coordinan el crecimiento y la formación de patrón del esbozo de extremidad a lo largo de tres ejes, el eje P-D, el eje A-P y el eje D-V. Tres son los centros señalizadores más importantes. La cresta ectodérmica apical (AER), un engrosamiento del ectodermo en la parte más apical del esbozo de extremidad y que controla la formación de patrón en el eje P-D y cuya función está mediada por varios miembros de la familia de los FGFs. La zona de actividad polarizadora (ZPA), localizada en el mesodermo posterior del esbozo de extremidad y con función señalizadora en el eje A-P, mediada por la proteína SHH. El ectodermo no- AER que controla la formación de patrón en el eje D-V y en cuya función son fundamentales las señalizaciones por WNT y BMPs, miembros estos últimos de la superfamilia de los TGFs. El esbozo de extremidad crece y se alarga a lo largo del P-D. Primero las células mesodérmicas se condensan y se diferencian a cartílago que, posteriormente es sustituido por hueso. Se van formando progresivamente tres segmentos el proximal o estilopodio, el intermedio o zeugopodio y, Los genes HOX son una familia altamente conservada de factores de transcripción que controlan el desarrollo embrionario en todos los animales. Los mamíferos tienen 39 genes Hox organizados en cuatro clusters (HoxA, HoxB, HoxC y HoxD), cada uno conteniendo de 9 a 11 genes. Durante el desarrollo de la extremidad los clusters A y D desempeñan papeles fundamentales en la formación de patrón a lo largo de los tres ejes, aunque se ha estudiado más su papel en los ejes P-D y A-P. La especificación de los tres segmentos P-D está acompañada por un patrón específico de expresión de los genes 5'de los clusters A y D. Experimentos de pérdida de función en ratón han mostrado la existencia de una asociación entre determinadas proteínas HOX y cada uno de los segmentos próximo distales. Por ejemplo, parálogos del grupo 11 y parálogos del grupo 13 son absolutamente necesarios para la formación de patrón del zeugopodio y autopodio respectivamente. Los fenotipos de ratones mutantes con pérdida de función de alelos de los grupos 11, 12 y 13 pertenecientes a los cluster HOXA y HOXD, permite suponer que los 5'Hox están implicados en el control del número de dedos. Por otro lado, trabajos recientes, han puesto de manifiesto la conexión entre los genes Hox y las vías señalizadoras más importantes para el desarrollo de la extremidad. Por ejemplo, se sabe que las proteínas HOX controlan la transcripción de Shh y que se unen físicamente a GLI3 (mediador de la actividad de SHH), y a SMADs (mediadores de la actividad de los BMPs) y modulan su actividad. Como señalamos anteriormente, el crecimiento y formación de patrón del esbozo de extremidad a lo largo de los ejes P-D y A-P está controlado por la señalización de los FGFs de la AER y por SHH de la ZPA respectivamente. Un bucle de retroalimentación positivo que se establece entre la AER-FGFs y ZPA-SHH es fundamental para este proceso y para el mantenimiento de los propios centros señalizadores. La pérdida de alguna señal lleva a la downregulaci

The formation and maintenance of the apical ectodermal ridge (AER) is critical for the outgrowth and patterning of the vertebrate limb. In the present work, we have investigated the role of Epiprofin (Epfn/Sp6), a member of the SP/KLF transcription factor family that is expressed in the limb ectoderm and the AER, during limb development. Epfn mutant mice have a defective autopod that shows mesoaxial syndactyly in the forelimb and synostosis (bony fusion) in the hindlimb and partial bidorsal digital tips. Epfn mutants also show a defect in the maturation of the AER that appears flat and broad, with a double ridge phenotype. By genetic analysis, we also show that Epfn is controlled by WNT/b-CATENIN signaling in the limb ectoderm. Since the less severe phenotypes of the conditional removal of b-catenin in the limb ectoderm strongly resemble the limb phenotype of Epfn mutants, we propose that EPFN very likely functions as a modulator of WNT signaling in the limb ectoderm.

El presente libro recopila los informes analíticos desarrollados por un grupo de profesores de la Facultad de Adminstración y Contabilidad de la Universidad del Pacífico, sobre las buenas prácticas de gobierno corporativo que vienen aplicando en nuestro país empresas como Backus, Graña y Montero, Incasur, Profuturo AFP y Red de Energía del Perú. Mediante estos informes, queremos mostrar al lector cómo las experiencias y buenas prácticas de gobierno corporativo de dichas empresas marcan pautas importantes en el desarrollo de los diversos sectores económicos así como del país, lo que genera un efecto multiplicador positivo en las políticas tanto sociales como económicas del gobierno en general.

Normal patterning of tissues and organs requires the tight restriction of signaling molecules to well-defined organizing centers. In the limb bud, one of the main signaling centers is the zone of polarizing activity (ZPA) that controls growth and patterning through the production of sonic hedgehog (SHH). The appropriate temporal and spatial expression of Shh is crucial for normal limb bud patterning, because modifications, even if subtle, have important phenotypic consequences. However, although there is a lot of information about the factors that activate and maintain Shh expression, much less is known about the mechanisms that restrict its expression to the ZPA. In this study, we show that BMP activity negatively regulates Shh transcription and that a BMP-Shh negative-feedback loop serves to confine Shh expression. BMP-dependent downregulation of Shh is achieved by interfering with the FGF and Wnt signaling activities that maintain Shh expression. We also show that FGF induction of Shh requires protein synthesis and is mediated by the ERK1/2 MAPK transduction pathway. BMP gene expression in the posterior limb bud mesoderm is positively regulated by FGF signaling and finely regulated by an auto-regulatory loop. Our study emphasizes the intricacy of the crosstalk between the major signaling pathways in the posterior limb bud.

Several members of the FGF gene family have been shown to intervene from various tissue sources to direct otic placode induction and otic vesicle formation. In this study we define the roles of FGF8, found in different expression domains during this process, in mice and chickens. By conditional inactivation of Fgf8 in distinct tissue compartments we demonstrate that Fgf8 is required in the mesoderm and endoderm during early inner ear development. In the chicken embryo, overexpression of Fgf8 from various tissue sources during otic specification leads to a loss of otic tissue. In contrast ectopic overexpression of Fgf10, a major player during murine otic induction, does not influence otic vesicle formation in chicken embryos but results in the formation of ectopic structures with a non-otic character. This study underlines the crucial role of a defined Fgf8 expression pattern controlling inner ear formation in vertebrates. © 2009 Elsevier Ireland Ltd. All rights reserved.

The canonical Wnt and sonic hedgehog (Shh) pathways have been independently linked to cell proliferation in a variety of tissues and systems. However, interaction of these signals in the control of cell cycle progression has not been studied. Here, we demonstrate that in the developing vertebrate nervous system these pathways genetically interact to control progression of the G1 phase of the cell cycle. By in vivo loss-of-function experiments, we demonstrate the absolute requirement of an upstream Shh activity for the regulation of Tcf3/4 expression. In the absence of Tcf3/4, the canonical Wnt pathway cannot activate target gene expression, including that of cyclin D1, and the cell cycle is necessarily arrested at G1. In addition to the control of G1 progression, Shh activity controls the G2 phase through the regulation of cyclin E, cyclin A and cyclin B expression, and this is achieved independently of Wnt. Thus, in neural progenitors, cell cycle progression is co-ordinately regulated by Wnt and Shh activities.

Here we analyze limb development after the conditional inactivation of Fgf8 from the epiblast, using the previously described MORE (Mox2Cre) line. This line drives variable mosaic recombination of a floxed Fgf8 allele, resulting in a small proportion of AER cells that maintain Fgf8 expression. The phenotype of Mox2Cre:Fgf8 limbs is most similar to that of Msx2Cre;Fgf8 forelimbs, indicating that a small but durable expression of FGF8 is equivalent to an early normal, but transitory, expression. This functional equivalence likely relies on the subsequent Fgf4 upregulation that buffers the differences in the pattern of Fgf8 expression between the two conditional mutants. The molecular analysis of Mox2Cre;Fgf8 limbs shows that, despite Fgf4 upregulation, they develop under reduced FGF signaling. These limbs also exhibit an abnormal area of cell death at the anterior forelimb autopod, overlapping with an ectopic domain of Bmp7 expression, which can explain the abnormal morphogenesis of the anterior autopod. © 2008 Wiley-Liss, Inc.

A crucial issue in limb development is how a correct set of precisely shaped digits forms in the digital plate. This process relies on patterning across the anterior-posterior axis of the limb bud, which is under the control of Sonic hedgehog emanating from the zone of polarizing activity. Recently, Sonic hedgehog function in the limb bud has been shown to have a dual character controlling both growth and patterning of the digital field. This finding has prompted the proposal of new models of how these two functions are achieved, and this will be discussed in this review. © 2008 Elsevier Ltd. All rights reserved.

The Apical Ectodermal Ridge (AER) is one of the main signaling centers during limb development. It controls outgrowth and patterning in the proximo-distal axis. In the last few years a considerable amount of new data regarding the cellular and molecular mechanisms underlying AER function and structure has been obtained. In this review, we describe and discuss current knowledge of the regulatory networks which control the induction, maturation and regression of the AER, as well as the link between dorso-ventral patterning and the formation and position of the AER. Our aim is to integrate both recent and old knowledge to produce a wider picture of the AER which enhances our understanding of this relevant structure. © UBC Press.

En el presente trabajo se expone la conveniencia de crear unas directrices técnicas concretas por espacio de la Red Natura 2000 y actividad productiva, con el objetivo de superar el carácter norma- tivo y regulador del Plan de Gestión y así incentivar las buenas prácticas por parte del propietario privado. Como ejemplo se recoge el protocolo definido para elaborar planes técnicos de ordenación de pastos en el Lugar de Importancia Comunitaria (LIC): Sierra de Villafuerte (Murcia)

En el presente documento se muestra como se ha estructurado en redes la información ecológica y de gestión en el Parque Regional de Sierra Espuña (Murcia), para facilitar y agilizar el acceso a la misma. El objetivo es, en primer lugar, incorporar a la planificación anual y los proyectos los resulta- dos de los diferentes seguimientos que se realizan en el territorio (flora, fauna, hábitats...). Además de esto, se busca relacionar la evolución de las distintas variables ecológicas, entre ellas los indicado- res del estado de conservación favorable de hábitats y especies de las Directivas 92/43/CEE y 79/409 CEE , y las distintas prácticas de gestión desarrolladas, con el fin de determinar las más apropiadas

During limb development, Sonic hedgehog (SHH) and HOX proteins are considered among the most important factors regulating digit number and identity. SHH signaling prevents the processing of GLI3 into a short form that functions as a strong transcriptional repressor. Gli3 mutant limbs are characterized by a severe polydactyly and associated ectopic anterior expression of 5′Hoxd genes. To genetically determine the involvement of 5′Hoxd genes in the polydactyly of Gli3 mutants, we have generated a compound mutant that simultaneously removes the three most 5′-located Hoxd genes and Gli3. Remarkably, the limbs that form in the absence of all four of these genes show the most severe polydactyly so far reported in the mouse. The analysis of gene expression performed in compound mutants allows us to propose that the increase in the number of digits is mediated by the gain in function of Hoxd10 and Hoxd9. Our results also support the notion that an adequate balance between positive and negative effects of different Hoxd genes is required for pentadactyly. © 2007 Elsevier Inc. All rights reserved.

Objetivo. Conocer la opinión de los formadores (tutores y colaboradores docentes) de los residentes de tercer año de medicina familiar y comunitaria (MFyC) sobre su propia actividad como docentes en aspectos relacionados con la formación, las habilidades y las cualidades necesarias para la docencia y las relaciones interprofesionales actuales y necesarias en un equipo de atención primaria con actividad docente. Diseño. Estudio cualitativo desarrollado entre junio de 2000 y mayo de 2002. Realización de un diseño muestral con población voluntaria. Emplazamiento. Unidad docente de MFyC de la Gerencia de Atención Primaria de Murcia. Participantes y/o contextos. Tutores y colaboradores docentes del programa de la residencia de MFyC. Método. Entrevista semiestructurada para la recogida de información. Análisis de contenido para la construcción de resultados a partir del análisis semiológico del discurso textual. Devolución sistemática de los resultados. Resultados. La pertenencia al equipo docente es la mayor motivación para participar en la docencia. Esta última aporta más ventajas para los tutores (afectivas, descarga asistencial) que dificultades (adaptación organizativa). El perfil del tutor se sustenta en las cualidades cientificotécnicas y personales, y el de las enfermeras, en las comunitarias. La colaboración entre enfermera y tutor es informal y las estrategias docentes más empleadas por el tutor son la orientación, la guía y el fomento de la autonomía del residente. La enfermera colabora con la docencia transmitiendo un modelo de desarrollo profesional y facilitando el trabajo en equipo. Conclusiones. Resalta la complejidad existente en el proceso formativo. La formación de posgrado de MFyC es transprofesional y no se circunscribe exclusivamente a la relación docente entre tutores y residentes. El paradigma cualitativo se manifiesta útil para obtener una visión del proceso docente desde la perspectiva de diferentes actores., Objective. To find the view of trainers (tutors and teaching assistants) of third-year family and community medicine (FCM) residents concerning their own teaching activity in areas such as training, the skills and qualities required to be a teacher and the inter-professional relationships that are current and that are needed in a primary care teaching team. Design. Qualitative study developed between June 2000 and May 2002. Sample design with a volunteer population. Setting. FCM teaching unit under the Primary Care Administration of Murcia. Participants and/or contexts. Tutors and teaching assistants in the FCM residents' programme. Method. Semi-structured interview for information gathering. Contents analysis to construct results on the basis of the semiological analysis of the textual discourse. Systematic return of the results. Results. Belonging to the teaching team is the highest motivation for taking part in teaching. It gives the tutors more benefits (affective, care load) than difficulties (organisational adaptation). The tutor profile is sustained by his/her scientific-technical and personal qualities; that of the nurse, by his/her community qualities. Collaboration between nurse and tutor is informal and the teaching strategies most employed by tutors are guidance, guide-lines and encouragement of residents' autonomy. Nurses collaborate with teaching by transmitting a model of professional development and facilitating teamwork. Conclusions. The complexity of the training process stands out. Postgraduate FCM training is cross-professional, not exclusively circumscribed by the tutor-resident teaching relationship. The qualitative paradigm is shown to be useful for obtaining a vision of the teaching process from the perspective of different actors.

In this investigation, the relationship between antisocial behavior in adolescents and various aspects of personal control is analyzed. Two instruments were administered to 324 young people (167 boys and 157 girls): Seisdedos’ (1987) Antisocial and Criminal Behavior Scale A-D, to evaluate socially disorientated behavior, and the Infantile and Adolescent Self-Control Questionnaire, CACIA; Capafons y Silva, (1986), a personal self-assessment scale that evaluates four dimensions of personal control and indicates adolescents’ ability to self-evaluate themselves, delay gratification, endure negative situations, and use self-rewards and punishments. The results show significant statistical relationships between socially maladaptive behavior and the self-control components evaluated. The most deficient variable in these young people was their ability to delay gratification, which was established as the only aspect of personal self-regulation that predicted antisocial and criminal behavior among the girls. With regard to the boys, three variables were significant: in addition to their lack of delayed gratification, self-gratification problems, and the inability to endure painful and disagreeable situations were also observed., En esta investigación se analizan las relaciones entre el comportamiento antisocial en adolescentes y diferentes aspectos del autocontrol personal. A 324 jóvenes ( 167 chicos y 157 chicas), se les administraron dos pruebas, una para la valoración de la conducta desadaptada socialmente, la escala de Conducta Antisocial y Delictiva de Seisdedos, A-D (1987), y otra de autocalificación personal, el Cuestionario de Autocontrol Infantil y Adolescente de Capafóns y Silva, CACIA (1986), que evalúa cuatro dimensiones de autocontrol, indicando la habilidad de los adolescentes para autoevaluarse, retardar la gratificación, soportar situaciones negativas y utilizar autorecompensas y castigos. Los resultados muestran relaciones estadísticas significativas entre el comportamiento desviado socialmente y los diferentes componentes del autocontrol evaluados. El retardo de la recompensa es la variable más deficitaria en estos jóvenes, estableciéndose como el único aspecto de la autorregulación personal, predictivo de las conductas antisociales y delictivas en las chicas. Respecto a los chicos, son tres las variables significativas, ya que junto al retardo de la gratificación, encontramos los problemas en autogratificación, así como la incapacidad para soportar situaciones dolorosas y desagradables.