Dorsal hindbrain ablation results in rerouting of neural crest migration and changes in gene expression, but normal hyoid development

Our previous studies have shown that hindbrain neural tube cells can regulate to form neural crest cells for a limited time after neural fold removal (Scherson, T., Serbedzija, G., Fraser, S. E. and Bronner-Fraser, M. (1993). Development 188, 1049-1061; Sechrist, J., Nieto, M. A., Zamanian, R. T. and Bronner-Fraser, M. (1995). Development 121, 4103-4115). In the present study, we ablated the dorsal hindbrain at later stages to examine possible alterations in migratory behavior and/or gene expression in neural crest populations rostral and caudal to the operated region. The results were compared with those obtained by misdirecting neural crest cells via rhombomere rotation. Following surgical ablation of dorsal r5 and r6 prior to the 10 somite stage, r4 neural crest cells migrate along normal pathways toward the second branchial arch. Similarly, r7 neural crest cells migrate primarily to the fourth branchial arch. When analogous ablations are performed at the 10- 12 somite stage, however, a marked increase in the numbers of DiI/Hoxa-3-positive cells from r7 are observed within the third branchial arch. In addition, some DiI-labeled r4 cells migrate into the depleted hindbrain region and the third branchial arch. During their migration, a subset of these r4 cells up-regulate Hoxa-3, a transcript they do not normally express. Krox20 transcript levels were augmented after ablation in a population of neural crest cells migrating from r4, caudal r3 and rostral r3. Long-term survivors of bilateral ablations possess normal neural crest-derived cartilage of the hyoid complex, suggesting that misrouted r4 and r7 cells contribute to cranial derivatives appropriate for their new location. In contrast, misdirecting of the neural crest by rostrocaudal rotation of r4 through r6 results in a reduction of Hoxa-3 expression in the third branchial arch and corresponding deficits in third arch-derived structures of the hyoid apparatus. These results demonstrate that neural crest/tube progenitors in the hindbrain can compensate by altering migratory trajectories and patterns of gene expression when the adjacent neural crest is removed, but fail to compensate appropriately when the existing neural crest is misrouted by neural tube rotation

Rhombomere of origin determines autonomous versus environmentally regulated expression of Hoxa3 in the avian embryo

We have investigated the pattern and regulation of Hoxa3 expression in the hindbrain and associated neural crest cells in the chick embryo, using whole mount in situ hybridization in conjunction with DiI labeling of neural crest cells and microsurgical manipulations. Hoxa3 is expressed in the neural plate and later in the neural tube with a rostral border of expression corresponding to the boundary between rhombomeres (r) 4 and 5. Initial expression is diffuse and becomes sharp after boundary formation. Hoxa3 exhibits uniform expression within r5 after formation of rhombomeric borders. Cell marking experiments reveal that neural crest cells migrating caudally, but not rostrally, from r5 and caudally from r6 express Hoxa3 in normal embryo. Results from transposition experiments demonstrate that expression of Hoxa3 in r5 neural crest cells is not strictly cell-autonomous. When r5 is transposed with r4 by rostrocaudal rotation of the rhomobomeres, Hoxa3 is expressed in cells migrating lateral to transposed r5 and for a short time, in condensing ganglia, but not by neural crest within the second branchial arch. Since DiI-labeled cells from transposed r5 are present in the second arch, Hoxa3-expressing neural crest cells from r5 appear to down-regulate their Hoxa3 expression in their new environment. In contrast, when r6 is transposed to the position of r4 after boundary formation, Hoxa3 is maintained in both migrating neural crest cells and those positioned within the second branchial arch and associated ganglia. These results suggest that Hoxa3 expression is cell-autonomous in r6 and its associated neural crest. Our results suggest that neural crest cells expressing the same Hox gene are not eqivalent; they respond differently to environmental signals and exhibit distinct degrees of cell autonomy depending upon their rhombomere of origin

LAND REFORM AND DEFORESTATION IN THE BRAZILIAN AMAZONIA

No processo de reforma agrária brasileiro é comum a redistribuição de terra ocorrer por meio de invasões das grandes proprieades pelos sem terra. Esse mecanismo introduz insegurança no direito de propriedade fundiária e, na Regîão Amazônica, tem como consequência o excesso de desflorestamento. Esse trabalho utiliza um jogo não-cooperativo para mostrar que as interações estratégicas entre proprietários e posseiros em um contexto instittucional onde as florestas naturais são consideradas como recursos de livre acesso implicam o excesso de desflorestamento. A principal implicação analítica do modelo é que a taxa de desflorestamento de determinada área tende a aumentar com o número de posseiros na área. Essa implicação é confirmada quando testada em um painel de dados censitários municipais da Amazônia brasileira no período 1970-96 e esse resultado se mantem mesmo quando se controla o problema da endogeneidade do número de posseiros na especificação de uma equação de desflorestamento. Da perspectiva ambiental, portanto, o resultado permite questionar os mecanismos utilizados pelas políticas de reforma agrária no Brasil.----------------------------------------In Brazil, the land reform involves redistribution of land plots from large landowners to squatters. It generates property rights insecurity which alters land uses and fosters forest depletion. In this paper, a non cooperative game model is developed where natural forests are considered as an open access resource and the strategic interactions between landowners and squatters lead to an over deforestation. The main theoretical implication is a positive impact of squatters on deforestation. It is successfully tested on a panel data set covering the municipalities of the Legal Amazonia controlling for the endogeneity of squatters in a deforestation equation. The result questions the modalities of the Brazilian state-led land reformreforma agrária, desflorestamento, insegurança dos direitos de propriedade, econometria de painel, Land reform, Deforestation, land tenure insecurity, panel estimation, Land Economics/Use,

Genotype imputation accuracy in a F2 pig population using high density and low density SNP panels

Background: F2 resource populations have been used extensively to map QTL segregating between pig breeds. A limitation associated with the use of these resource populations for fine mapping of QTL is the reduced number of founding individuals and recombinations of founding haplotypes occurring in the population. These limitations, however, become advantageous when attempting to impute unobserved genotypes using within family segregation information. A trade-off would be to re-type F2 populations using high density SNP panels for founding individuals and low density panels (tagSNP) in F2 individuals followed by imputation. Subsequently a combined meta-analysis of several populations would provide adequate power and resolution for QTL mapping, and could be achieved at relatively low cost. Such a strategy allows the wealth of phenotypic information that has previously been obtained on experimental resource populations to be further mined for QTL identification. In this study we used experimental and simulated high density genotypes (HD-60K) from an F2 cross to estimate imputation accuracy under several genotyping scenarios. Results: Selection of tagSNP using physical distance or linkage disequilibrium information produced similar imputation accuracies. In particular, tagSNP sets averaging 1 SNP every 2.1 Mb (1,200 SNP genome-wide) yielded imputation accuracies (IA) close to 0.97. If instead of using custom panels, the commercially available 9K chip is used in the F2, IA reaches 0.99. In order to attain such high imputation accuracy the F0 and F1 generations should be genotyped at high density. Alternatively, when only the F0 is genotyped at HD, while F1 and F2 are genotyped with a 9K panel, IA drops to 0.90. Conclusions: Combining 60K and 9K panels with imputation in F2 populations is an appealing strategy to re-genotype existing populations at a fraction of the cost.Fil: Gualdron Duarte, Jose Luis. Michigan State University; Estados Unidos. Universidad de Buenos Aires. Facultad de Agronomia. Departamento de Producción Animal; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Bates, Ronald O.. Michigan State University; Estados UnidosFil: Ernst, Catherine W.. Michigan State University; Estados UnidosFil: Raney, Nancy E.. Michigan State University; Estados UnidosFil: Cantet, Rodolfo Juan Carlos. Universidad de Buenos Aires. Facultad de Agronomia. Departamento de Producción Animal; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Steibel, Juan P.. Michigan State University; Estados Unido

Evaluacion de los canones neoclasicos faciales en adultos jovenes sanos estudiantes de Universidad de Talca

81 p.El propósito de este estudio fue evaluar los parámetros faciales de la población chilena para compararlos con los cánones neoclásicos y proporcionar información necesaria para la identificación médico legal, cirugía plástica y estética. Las reglas que definen la relación entre varias áreas de la cabeza y la cara fueron formuladas por estudiantes y artistas del renacimiento. Basados en los cánones griegos básicos. En la medicina el uso de las fórmulas neoclásicas fueron propagadas por artistasanatomistas del siglo diecisiete al diecinueve. La importancia de ver la cara en proporciones ha sido enfatizada por muchos cirujanos. Los cánones neoclásicos son conocidos por los cirujanos plásticos modernos, sin embargo su uso en la panificación quirúrgica han sido limitados al rol de guías de trabajo. El objetivo de este estudio es determinar cánones faciales característicos en adultos jóvenes sanos estudiantes de la Universidad de Talca. En este estudio participaron individuos Chilenos de ambos sexos, perteneciente a la Escuela de Odontología de la Universidad de Talca, con un total de 140 personas, 70 hombres y 70 mujeres, cuya edad fluctúa entre los 18 y los 30 años. Para determinar los 8 cánones neoclásicos se utilizó antropometría indirecta mediante 2 fotografías, frente y perfil, estas fueron captadas a través de una cámara digital Cyber Shot 7.2 y para asegurar la uniformidad y estandarización de las imágenes se utilizó una regla milimetrada. Obtenidas las imágenes estas se analizaron en el programa Antrophmeter que reproduce las imágenes en tamaño real. Los resultados se agruparon en tablas, en las cuales se describen las variables estudiadas y valores obtenidos en milímetros. Luego se analizó en el programa SPSS 15.0, con la finalidad de obtener la frecuencia de las proporciones y sus variaciones. El análisis estadísticamente descriptivo arrojó que existen cánones faciales característicos para los adultos jóvenes sanos estudiantes de la Universidad de Talca. Presentándose cánones faciales frecuentes tales como la distancias entre vertexendocanthion aumentada, nasión-subnasión disminuida, vertex-triquion y triquion-glabela disminuida, suprauricular-subauricular aumentado, alar-alar aumentado para quinto, séptimo y octavo parámetro. El parámetro con mayor equivalencia es el sexto donde la distancia endocanthion-endocanthion es muy similar a la distancia endocanthionexocanthion

Perspectives of key stakeholders on the bi-national agreement between Argentina and Chile concerning the eradication of North American beavers and the restoration of affected ecosystems

In 2008, Argentina and Chile signed an agreement to eradicate North American beavers (Castor canadensis) and restore degraded forests. The plans and actions related to this treaty have been conducted principally by experts with biological knowledge, paying scant attention to social aspects. From a socio-ecological approach, we evaluated the perspectives of two groups of key stakeholders (managers and researchers) from Argentinean and Chilean institutions. Via surveys, we compared i) attitudes towards the binational agreement’s two objectives (eradication and restoration), ii) the reasons that underlie these positions, and iii) the opinions about obstacles in implementing the agreement. The majority of both groups agreed with the two objectives, nonetheless managers supported more the eradication of the beaver and researchers supported more the restoration of degraded forests. These positions were based on biological arguments (e.g., ecological harm, being an exotic species), more than on social ones (e.g., ethics, economic impact). Paradoxically, managers and researchers identified the lack of information on social topics (e.g., internal management, interinstitutional cooperation, financing) as the main obstacle for the implementation of the agreement. While there was a high level of consensus, dissident positions were found among these stakeholders, whose profile is rather homogeneous. Managers particularly emphasized politico-institutional topics. Consequently, we are called upon to deepen and increase attention towards social dimensions in the approach to biological invasions to diversify the perspectives towards the problem, as well as to optimize and improve outcomes of potential actions in complex and heterogeneous societies.Fil: Anderson, Christopher Brian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina. Universidad Nacional de Tierra del Fuego; ArgentinaFil: Roulier, Catherine Solange. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina. Universidad Nacional de Tierra del Fuego; ArgentinaFil: Pizarro Pinochet, Jose Cristobal. Universidad de Concepción; Chile. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentin