Spatial expression of Hox cluster genes in the ontogeny of a sea urchin

The Hox cluster of the sea urchin Strongylocentrous purpuratus contains ten genes in a 500 kb span of the genome. Only two of these genes are expressed during embryogenesis, while all of eight genes tested are expressed during development of the adult body plan in the larval stage. We report the spatial expression during larval development of the five 'posterior' genes of the cluster: SpHox7, SpHox8, SpHox9/10, SpHox11/13a and SpHox11/13b. The five genes exhibit a dynamic, largely mesodermal program of expression. Only SpHox7 displays extensive expression within the pentameral rudiment itself. A spatially sequential and colinear arrangement of expression domains is found in the somatocoels, the paired posterior mesodermal structures that will become the adult perivisceral coeloms. No such sequential expression pattern is observed in endodermal, epidermal or neural tissues of either the larva or the presumptive juvenile sea urchin. The spatial expression patterns of the Hox genes illuminate the evolutionary process by which the pentameral echinoderm body plan emerged from a bilateral ancestor

Hindgut specification and cell-adhesion functions of Sphox11/13b in the endoderm of the sea urchin embryo

Sphox11/13b is one of the two hox genes of Strongylocentrotus purpuratus expressed in the embryo. Its dynamic pattern of expression begins during gastrulation, when the transcripts are transiently located in a ring of cells at the edge of the blastopore. After gastrulation, expression is restricted to the anus–hindgut region at the boundary between the ectoderm and the endoderm. The phenotype that results when translation of Sphox11/13b mRNA is knocked down by treatment with morpholino antisense oligonucleotides (MASO) suggests that this gene may be indirectly involved in cell adhesion functions as well as in the proper differentiation of the midgut–hindgut and midgut–foregut sphincters. The MASO experiments also reveal that Sphox11/13b negatively regulates several downstream endomesoderm genes. For some of these genes, Sphox11/13b function is required to restrict expression to the midgut by preventing ectopic expression in the hindgut. The evolutionary conservation of these functions indicates the general roles of posterior Hox genes in regulating cell-adhesion, as well as in spatial control of gene regulatory network subcircuits in the regionalizing gut

Trade Intensity and Business Cycle Synchronization: Are Developing Countries any Different?

Some key criteria in the optimal currency area literature are that countries should join a currency union if they have closer international trade links and more symmetric business cycles. However, both criteria are endogenous. Frankel and Rose (1998) find that trade intensity increases cycle correlation among industrial countries. We study whether the same result holds true for the case of developing countries, as their different patterns of international trade and specialization may lead to cyclical asymmetries among them and between industrial and developing countries. We gather annual information for 147 countries for 1960-99 (33,676 country pairs) and find: (i) countries with higher bilateral trade exhibit higher business cycle synchronization, with an increase of one standard deviation in bilateral trade intensity raising the output correlation from 0. 05 to 0. 09 for all country pairs; (ii) countries with more asymmetric structures of production exhibit a smaller business cycle correlation; (iii) the impact of trade integration on business cycles is higher for industrial countries than both developing and industrial-developing country pairs; (iv) a one standard deviation increase in bilateral trade intensity leads to surges in output correlation from 0. 25 to 0. 39 among industrial countries, from 0. 08 to 0. 10 for our sample of industrial-developing country pairs, and from 0. 03 to 0. 06 among developing countries; (v) the impact of trade intensity on cycle correlation is smaller the greater the production structure asymmetries between the countries.

From Zn to Mn: the study of novel manganese-binding groups in the search for new drugs against tuberculosis.

In most eubacteria, apicomplexans, and most plants, including the causal agents for diseases such as malaria, leprosy, and tuberculosis, the methylerythritol phosphate pathway is the route for the biosynthesis of the C(5) precursors to the essential isoprenoid class of compounds. Owing to their absence in humans, the enzymes of the methylerythritol phosphate pathway have become attractive targets for drug discovery. This work investigates a new class of inhibitors against the second enzyme of the pathway, 1-deoxy-D-xylulose 5-phosphate reductoisomerase. Inhibition of this enzyme may involve the chelation of a crucial active site Mn ion, and the metal-chelating moieties studied here have previously been shown to be successful in application to the zinc-dependent metalloproteinases. Quantum mechanics and docking calculations presented in this work suggest the transferability of these metal-chelating compounds to Mn-containing 1-deoxy-D-xylulose 5-phosphate reductoisomerase enzyme, as a promising starting point to the development of potent inhibitors

Imaginários e discursos de professores sobre leitura no ensino de ciências/geociências : algumas condições de produção

Pautado em aportes da Análise de Discurso de origem francesa, pressupondo que o professor tem papel fundamental na mediação da leitura e na formação do leitor de ciência, e que essa mediação se relaciona com seus imaginários, este trabalho teve como objetivo compreender aspectos das condições de produção dos imaginários de quatro professores de diferentes disciplinas de uma mesma escola sobre leitura no ensino de ciências. Apontamos que seus imaginários sobre leitura se relacionam às seguintes condições de produção: suas memórias, familiares e escolares, enquanto leitores e os discursos sobre leitura que têm chegado às escolas por meio de documentos oficiais e cursos de formação continuada. Discutimos implicações para a formação de professores: a importância de trabalhar suas memórias enquanto leitores e os sentidos sobre leitura que já circulam nas escolas

Non-gaussianity at tree and one-loop levels from vector field perturbations

We study the spectrum P_\zeta and bispectrum B_\zeta of the primordial curvature perturbation \zeta when the latter is generated by scalar and vector field perturbations. The tree-level and one-loop contributions from vector field perturbations are worked out considering the possibility that the one-loop contributions may be dominant over the tree level terms (both (either) in P_\zeta and (or) in B_\zeta) and viceversa. The level of non-gaussianity in the bispectrum, f_{NL}, is calculated and related to the level of statistical anisotropy in the power spectrum, g_\zeta. For very small amounts of statistical anisotropy in the power spectrum, the level of non-gaussianity may be very high, in some cases exceeding the current observational limit.Comment: LaTeX file, 11 pages, Main body: 8 pages, References: 3 pages. v2: Minor corrections. References added. Conclusions unchanged. v3: Minor corrections. Some references added and others updated. Version accepted for publication in Physical Review

Turbulence and Chaos in Anti-de-Sitter Gravity

Due to the AdS/CFT correspondence the question of instability of Anti-de-Sitter spacetimes sits in the intersection of mathematical and numerical relativity, string theory, field theory and condensed matter physics. In this essay we revisit that important question emphasizing the power of spectral methods and highlighting the effectiveness of standard techniques for studying nonlinear dynamical systems. In particular we display explicitly how the problem can be modeled as a system on nonlinearly coupled harmonic oscillators. We highlight some of the many open questions that stem from this result and point out that a full understanding will necessarily required the interdisciplinary cooperation of various communities.Comment: 6 pages, 12 figures. Essay awarded honorable mention in the Gravity Research Foundation essay competition 201