Current perspectives of the signaling pathways directing neural crest induction.

The neural crest is a migratory population of embryonic cells with a tremendous potential to differentiate and contribute to nearly every organ system in the adult body. Over the past two decades, an incredible amount of research has given us a reasonable understanding of how these cells are generated. Neural crest induction involves the combinatorial input of multiple signaling pathways and transcription factors, and is thought to occur in two phases from gastrulation to neurulation. In the first phase, FGF and Wnt signaling induce NC progenitors at the border of the neural plate, activating the expression of members of the Msx, Pax, and Zic families, among others. In the second phase, BMP, Wnt, and Notch signaling maintain these progenitors and bring about the expression of definitive NC markers including Snail2, FoxD3, and Sox9/10. In recent years, additional signaling molecules and modulators of these pathways have been uncovered, creating an increasingly complex regulatory network. In this work, we provide a comprehensive review of the major signaling pathways that participate in neural crest induction, with a focus on recent developments and current perspectives. We provide a simplified model of early neural crest development and stress similarities and differences between four major model organisms: Xenopus, chick, zebrafish, and mouse

Science with the World Space Observatory - Ultraviolet

The World Space Observatory-Ultraviolet (WSO-UV) will provide access to the UV range during the next decade. The instrumentation on board will allow to carry out high resolution imaging, high sensitivity imaging, high resolution (R~55000) spectroscopy and low resolution (R~2500) long slit spectroscopy. In this contribution, we briefly outline some of the key science issues that WSO-UV will address during its lifetime. Among them, of special interest are: the study of galaxy formation and the intergalactic medium; the astronomical engines; the Milky Way formation and evol ution, and the formation of the Solar System and the atmospheres of extrasolar p lanets.Comment: Just one text file (aigomezdecastro.tex). To be published in the proceeding of the conference: "New Quest in Stellar Astrophysics II: UV properties of evolved stellar populations" held in Puerto Vallarta - Mexico, in april 200

Changes in Nerve Conduction Studies Predate Clinical Symptoms Onset in Early Onset Val30Met Hereditary ATTR Amyloidosis

Background and purpose: Hereditary amyloidosis related to transthyretin (ATTR) is a rare and progressive disease that, despite the phenotypic heterogeneity, a length-dependent sensorimotor axonal neuropathy (ATTR-PN) is the classic hallmark. Timely diagnosis is paramount for early treatment implementation. Methods: Sixty-nine asymptomatic gene carriers (Val30Met) were assessed during a 4-year period to identify those remaining asymptomatic versus those converting to ATTRV30M-PN. Conversion to symptomatic was defined as presenting with two definite symptoms of ATTRV30M-PN. Composite neurophysiological scores of sensory (SNS), motor (MNS), and sympathetic skin response (SSRS) amplitudes were used to assess neuropathy progression. We used mixed-effects modeling and ordinal logistic regression to assess neurophysiological evolution over time. Results: Of all asymptomatic gene carriers, 55.1% (n = 38/69) converted over the period of this analysis. The progression of the SNS relative to baseline was different between groups (asymptomatic gene carriers vs. converters), the decline being greater in the converter group (time × group interaction p = 0.040), starting about 2 years before symptom onset. No significant change occurred regarding MNS or SSRS. Moreover, the percentage of cases with an annual decline on the SNS of at least 25%, gradually and significantly increased in the converter group, representing a 1.92 increase in risk of developing symptoms for those with such reduction on the last evaluation. Conclusions: A simple composite neurophysiological sum score can predict the onset of ATTRV30M-PN symptoms by as much as 2 years, highlighting the importance of a systematic follow-up of asymptomatic gene carriers, allowing a timely diagnosis, and management of symptomatic disease.info:eu-repo/semantics/publishedVersio

HREM studies of intergrowths in Sr2[Srn-1TinO3n+1] Ruddlesden-Popper phases synthesized by mechanochemical activation

A mechanochemical activation route has been applied in order to obtain the <i>n</i>=1–4 and ∞ members of the Sr<sub>2</sub>[Sr<sub>n</sub><sub>−1</sub>Ti<sub>n</sub>O<sub>3n+1</sub>] Ruddlesden– Popper series from different (<i>n</i>+1)SrO:nTiO<sub>2</sub> mixtures. The mechanosynthesis of SrTiO<sub>3</sub> and Sr<sub>2</sub>TiO<sub>4</sub> was observed during the milling process from the initial stoichiometric mixture, but in the cases of the <i>n</i>=2–4 members, a subsequent thermal treatment was needed. The synthesis protocol of Sr<sub>3</sub>Ti<sub>2</sub>O<sub>7</sub> has been greatly improved and this compound can be isolated as a single, crystalline phase after annealing at 800°C. In the case of Sr<sub>4</sub>Ti<sub>3</sub>O<sub>10</sub> and Sr<sub>5</sub>Ti<sub>4</sub>O<sub>13</sub>, the formation temperature was also decreased, but members with <i>n</i>=3 and 4 could not be isolated. Detailed investigations using electron microscopy methods (TEM, HREM and SAED) were carried out in the samples corresponding to <i>n</i>=2–4. Although a single ordered Sr<sub>3</sub>Ti<sub>2</sub>O<sub>7</sub> structure is dominant in the sample corresponding to <i>n</i>=2, a few intergrowths of other Ruddlesden–Popper phases were observed. In the cases of <i>n</i>=3 and 4, the intergrowths of Ruddlesden–Popper phases are more frequent than in the <i>n</i>=2 composition and are randomly distributed in the sample. The more frequent occurrence of such stacking faults, with increasing <i>n</i> value, leads to a somewhat disordered layer stacking sequence

Detection of magnetic field in the B2 star ρ\rho Oph A with ESO FORS2

Circumstantial evidence suggests that magnetism and enhanced X-ray emission are likely correlated in early B-type stars: similar fractions of them ($\sim$ 10 %) are strong and hard X-ray sources and possess strong magnetic fields. It is also known that some B-type stars have spots on their surface. Yet up to now no X-ray activity associated with spots on early-type stars was detected. In this Letter we report the detection of a magnetic field on the B2V star $\rho$ Oph A. Previously, we assessed that the X-ray activity of this star is associated with a surface spot, herewith we establish its magnetic origin. We analyzed FORS2 ESO VLT spectra of $\rho$ Oph A taken at two epochs and detected a longitudinal component of the magnetic field of order of $\sim500$ G in one of the datasets. The detection of the magnetic field only at one epoch can be explained by stellar rotation which is also invoked to explain observed periodic X-ray activity. From archival HARPS ESO VLT high resolution spectra we derived the fundamental stellar parameters of $\rho$ Oph A and further constrained its age. We conclude that $\rho$ Oph A provides strong evidence for the presence of active X-ray emitting regions on young magnetized early type stars.Comment: 4 pages, 1 figure, 2 tables, accepted as a "Letter to the Editor" to Astronomy & Astrophysic