Showing 401 - 410 of 733 Items
Live imaging and biophysical modeling support a button-based mechanism of somatic homolog pairing in Drosophila
Date: 2021-06-01
Creator: Myron Child, Jack R. Bateman, Amir Jahangiri, Armando Reimer, Nicholas C., Lammers, Nica Sabouni, Diego Villamarin, Grace C. McKenzie-Smith, Justine E. Johnson, Daniel Jost, Hernan G. Garcia
Access: Open access
- 3D eukaryotic genome organization provides the structural basis for gene regulation. In Drosophila melanogaster, genome folding is characterized by somatic homolog pairing, where homologous chromosomes are intimately paired from end to end; however, how homologs identify one another and pair has remained mysterious. Recently, this process has been proposed to be driven by specifically interacting “buttons” encoded along chromosomes. Here, we turned this hypothesis into a quantitative biophysical model to demonstrate that a button-based mechanism can lead to chromosome-wide pairing. We tested our model using live-imaging measurements of chromosomal loci tagged with the MS2 and PP7 nascent RNA labeling systems. We show solid agreement between model predictions and experiments in the pairing dynamics of individual homologous loci. Our results strongly support a button-based mechanism of somatic homolog pairing in Drosophila and provide a theoretical framework for revealing the molecular identity and regulation of buttons.
Positive Effects of Nonnative Invasive Phragmites australis on Larval Bullfrogs
Date: 2012-08-30
Creator: Mary Rogalski
Access: Open access
islet reveals segmentation in the amphioxus hindbrain homolog
Date: 2000-04-01
Creator: William R. Jackman, James A. Langeland, Charles B. Kimmel
Access: Open access
- The vertebrate embryonic hindbrain is segmented into rhombomeres. Gene expression studies suggest that amphioxus, the closest invertebrate relative of vertebrates, has a hindbrain homolog. However, this region is not overtly segmented in amphioxus, raising the question of how hindbrain segmentation arose in chordate evolution. Vertebrate hindbrain segmentation includes the patterning of cranial motor neurons, which can be identified by their expression of the LIM-homeodomain transcription factor islet1. To learn if the amphioxus hindbrain homolog is cryptically segmented, we cloned an amphioxus gene closely related to islet1, which we named simply islet. We report that amphioxus islet expression includes a domain of segmentally arranged cells in the ventral hindbrain homolog. We hypothesize that these cells are developing motor neurons and reveal a form of hindbrain segmentation in amphioxus. Hence, vertebrate rhombomeres may derive from a cryptically segmented brain present in the amphioxus/vertebrate ancestor. Other islet expression domains provide evidence for amphioxus homologs of the pineal gland, adenohypophysis, and endocrine pancreas. Surprisingly, homologs of vertebrate islet1-expressing spinal motor neurons and Rohon-Beard sensory neurons appear to be absent. (C) 2000 Academic Press.
Invisible Women: Entrepreneurship, Innovation, and Family Firms in Nineteenth-Century France
Date: 2016-02-25
Creator: B. Zorina Khan
Access: Open access
- The French economy has been criticized for a lack of integration of women in business and for the prevalence of inefficient family firms. A sample drawn from patent and exhibition records is used to examine the role of women in enterprise and invention in France. Middle-class women were extensively engaged in entrepreneurship and innovation, and the empirical analysis indicates that their commercial efforts were significantly enhanced by association with family firms. Such formerly invisible achievements suggest a more productive role for family-based enterprises, as a means of incorporating relatively disadvantaged groups into the market economy as managers and entrepreneurs. This business model .... melds entrepreneurial passion with a long family tradition. - Wendel Company (1704-2014) 1
Exchange Rate Regimes and Nominal Wage Comovements in a Dynamic Ricardian Model
Date: 2013-10-28
Creator: Yao Tang, Yoshinori Kurokawa, Jiaren Pang
Access: Open access
- We construct a dynamic Ricardian model of trade with money and nominal exchange rate. The model implies that the nominal wages of the trading countries are more likely to exhibit stronger positive comovements when the countries fix their bilateral exchange rates. Panel regression results based on data from OECD countries from 1973 to 2012 suggest that countries in the European Monetary Union (EMU) experienced stronger positive wage comovements with their main trade partners. When we restrict the regression to the subsample of the EMU countries, we find a significant increase in wage comovements after these countries joined the EMU in 1999 compared to the pre-euro era. In comparison, when the sample is restricted to the non-EMU countries, we find no evidence that non-currency union pegs affected the wage comovements.
Large-scale chromosomal changes and associated fitness consequences in pathogenic fungi
Date: 2014-01-01
Creator: Anja Forche
Access: Open access
- Pathogenic fungi encounter many different host environments to which they must adapt rapidly to ensure growth and survival. They also must be able to cope with alterations in established niches during long-term persistence in the host. Many eukaryotic pathogens have evolved a highly plastic genome, and large-scale chromosomal changes including aneuploidy, and loss of heterozygosity (LOH) can arise under various in vitro and in vivo stresses. Both aneuploidy and LOH can arise quickly during a single cell cycle, and it is hypothesized that they provide a rapid, albeit imprecise, solution to adaptation to stress until better and more refined solutions can be acquired by the organism. While LOH, with the extreme case of haploidization in Candida albicans, can purge the genome from recessive lethal alleles and/or generate recombinant progeny with increased fitness, aneuploidy, in the absence or rarity of meiosis, can serve as a non-Mendelian mechanism for generating genomic variation. © Springer Science+Business Media 2014.
Saving our marine archives
Date: 2017-01-01
Creator: Emilie Dassié, Kristine Delong, Hali Kilbourne, Branwen Williams, Nerilie, Abram, Logan Brenner, Chloé Brahmi, Kim M. Cobb, Thierry Corrège, Delphine Dissard, Julien Emile-Geay, Heitor Evangelista, Michael N. Evans, Jesse Farmer, Thomas Felis, Michael Gagan, David P. Gillikin, Nathalie Goodkin, Myriam Khodri, Ana Carolina Lavagnino, Michèle Lavigne, Claire Lazareth, Braddock Linsley, Janice Lough, Helen McGregor, Intan S. Nurhati, Gilman Ouellette, Laura Perrin, Maureen Raymo, Brad Rosenheim, Michael Sandstrom, Bernd R. Schöne
Access: Open access
Un Sión tropical: el general Trujillo, Franklin Roosevelt y los judíos de Sosúa
Date: 2014-01-01
Creator: Allen Wells, Natalia Sanz González, (translator)
Access: Open access
- Setecientos cincuenta refugiados judíos dejaron la Alemania nazi y fundaron la colonia agrícola de Sosúa en la República Dominicana, que en ese momento estaba bajo el régimen de uno de los dictadores más represivos de Latinoamérica, el general Rafael Trujillo. En este libro, Allen Wells, hijo de uno de los colonos de Sosúa, cuenta la historia del general Trujillo, Franklin Delano Roosevelt y los afortunados pioneros que fundaron, en la costa norte de la isla, una exitosa cooperativa de productos lácteos de propiedad de los mismos empleados. ¿Por qué el dictador admitió a esos desesperados refugiados cuando muy pocas naciones aceptaron a los que escapaban del nazismo? Ansioso de mitigar las críticas internacionales después de que su Ejército masacrara varios miles de haitianos desarmados, Trujillo mandó a sus representantes a una conferencia sobre los refugiados del nazismo realizada en Évian, Francia, en 1938. Propuesta por Roosevelt para desviar las críticas a las políticas restrictivas de inmigración de su Gobierno, la Conferencia de Évian resultó un completo fracaso. La República Dominicana fue la única nación que aceptó abrir sus puertas; el oportunista Trujillo buscaba “blanquear” la población dominicana, recibiendo refugiados judíos, quienes en Europa eran ellos mismos sujeto de desprecio racista. Debido a que los Estados Unidos no admitieron números significativos de refugiados judíos, alentaron a Latinoamérica a aceptarlos. Esta propuesta, sumada a la preocupación mayor de Roosevelt de luchar contra el nazismo, fortaleció las relaciones estadounidenses con las dictaduras latinoamericanas en las décadas que vendrían.
Scattering equations and virtuous kinematic numerators and dual-trace functions
Date: 2014-01-01
Creator: Stephen G. Naculich
Access: Open access
- Inspired by recent developments on scattering equations, we present a constructive procedure for computing symmetric, amplitude-encoded, BCJ numerators for n-point gauge-theory amplitudes, thus satisfying the three virtues identified by Broedel and Carrasco. We also develop a constructive procedure for computing symmetric, amplitude-encoded dual-trace functions τ for n-point amplitudes. These can be used to obtain symmetric kinematic numerators that automatically satisfy color-kinematic duality. The S n symmetry of n-point gravity amplitudes formed from these symmetric dual-trace functions is completely manifest. Explicit expressions for four- and five-point amplitudes are presented. © 2014 The Author(s).
The structure of singularities in Π-minimizing networks in R2
Date: 1991-01-01
Creator: M. Alfaro, M. Conger, K. Hodges, A. Levy, R., Kochar, L. Kuklinski
Access: Open access