Showing 1721 - 1730 of 5709 Items
Evolution of pathogenicity and sexual reproduction in eight Candida genomes
Date: 2009-06-04
Creator: Geraldine Butler, Matthew D. Rasmussen, Michael F. Lin, Manuel A.S. Santos, Sharadha, Sakthikumar, Carol A. Munro, Esther Rheinbay, Manfred Grabherr, Anja Forche, Jennifer L. Reedy, Ino Agrafioti, Martha B. Arnaud, Steven Bates, Alistair J.P. Brown, Sascha Brunke, Maria C. Costanzo, David A. Fitzpatrick, Piet W.J. De Groot, David Harris, Lois L. Hoyer, Bernhard Hube, Frans M. Klis, Chinnappa Kodira, Nicola Lennard, Mary E. Logue, Ronny Martin, Aaron M. Neiman, Elissavet Nikolaou, Michael A. Quail, Janet Quinn, Maria C. Santos
Access: Open access
- Candida species are the most common cause of opportunistic fungal infection worldwide. Here we report the genome sequences of six Candida species and compare these and related pathogens and non-pathogens. There are significant expansions of cell wall, secreted and transporter gene families in pathogenic species, suggesting adaptations associated with virulence. Large genomic tracts are homozygous in three diploid species, possibly resulting from recent recombination events. Surprisingly, key components of the mating and meiosis pathways are missing from several species. These include major differences at the mating-type loci (MTL); Lodderomyces elongisporus lacks MTL, and components of the a1/α2 cell identity determinant were lost in other species, raising questions about how mating and cell types are controlled. Analysis of the CUG leucine-to-serine genetic-code change reveals that 99% of ancestral CUG codons were erased and new ones arose elsewhere. Lastly, we revise the Candida albicans gene catalogue, identifying many new genes. © 2009 Macmillan Publishers Limited. All rights reserved.
Spending Fast and Furious: Political Advertising in 2020
Date: 2021-03-01
Creator: Travis N. Ridout, Erika Franklin Fowler, Michael M. Franz
Access: Open access
- This article is a "first look"at political advertising in 2020. Spending on political advertising in the United States in 2020 obliterated records, and Democrats held huge advantages in the presidential race and in most congressional and senatorial races. In addition, all indicators suggest that spending on digital advertising continued to rise. Political advertising was largely similar in tone to past years and, in the presidential race, was substantially more positive than 2016. In addition, interest groups remained heavily involved in federal races in 2020, airing more ads than ever before, though their spending as a percentage of total ad spending was slightly less than in 2016. Political ad spending in 2020 may have been historically high because of the impact of COVID-19 on how campaigns could reach voters, suggesting that paid advertising may decline in 2022 and 2024, at least as a percentage of total election spending.
Peatlands and their role in the global carbon cycle
Date: 2011-04-20
Creator: Zicheng Yu, D. W. Beilman, S. Frolking, G. M. MacDonald, N. T., Roulet, P. Camill, D. J. Charman
Access: Open access
- Global peatlands store a very large carbon (C) pool located within a few meters of the atmosphere. Thus, peatland-atmosphere C exchange should be a major concern to global change scientists: Will large amounts of respired belowground C be released in a warmer climate, causing the climate to further warm (a positive climate feedback)? Will more C be sequestered due to increased plant growth in a warmer climate? How will land use change, fires, and permafrost thaw affect the magnitude and direction of carbon dioxide (CO ) and methane (CH ) exchange with the atmosphere? These questions remain challenging, but some significant progress has been made recently. 2 4
Does the neuropeptide GYS modulate stretch feedback pathways in the lobster cardiac neuromuscular system?
Date: 2014-08-01
Creator: Tricia Hartley
Access: Open access
- In many animals, there are groups of neurons, known as central pattern generators (CPGs), which are capable of controlling major everyday life functions. CPGs are responsible for functions that require patterned rhythmic activity, such as the heartbeat, digestion and locomotion. A CPG called the cardiac ganglion, consisting of only nine neurons, controls the rhythmic beating of the heart of the American lobster, Homarus americanus, by stimulating the muscle cells of the heart.My summer consisted of two separate projects in Patsy Dickinson’s neurophysiology lab, both studying the interaction of the cardiac ganglion with neuropeptides. These neuropeptides, GYSDRNYLRFamide (GYS) and SGRNFLRFamide (SGRN) are released hormonally into the cardiac neuromuscular system. The overarching goal of both projects was to determine the role of these neuropeptides in the lobster’s cardiac neuromuscular system.For my first project, I studied the interaction of the neuropeptide GYS with the stretch receptors of the lobster heart. Previous research has found these stretch receptors to be a form of excitatory feedback from the lobster heart to the cardiac ganglion, as heartbeat amplitude and frequency increase as heart is stretched. Further, the dendrites along the cardiac ganglion have been found to be stretch-sensitive, meaning when these dendrites were cut, this excitatory response is no longer observed. By stretching the heart with the dendrites intact and with GYS and next when the dendrites were cut and with GYS, the goal of this project was to determine if GYS would alter the feedback of the stretch receptors back to the cardiac ganglion to change heartbeat frequency and amplitude. Unfortunately, the intricacy involved in being able to cut the dendrites while allowing the heart to continue to beat proved very difficult and I moved on to my next project.The goal of my next project was to examine the interactions of the neuropeptides GYS and SGRN with the decreased and increased presence of nitric oxide, the second form of feedback from the heart muscle to the cardiac ganglion. Previous research shows nitric oxide as having an inhibitory effect, decreasing heartbeat amplitude and frequency. By applying both GYS and SGRN to both the isolated cardiac ganglion and the whole heart in the presence of both a nitric oxide inhibitor and donor, the hope is to be able to determine the interaction of these peptides with and without the presence of the feedback of nitric oxide. Because I started this project later in the summer, with the assistance of Sophie Janes’ data, I have been able to look at the effects of GYS on the whole heart, in addition to the combination of GYS with L-NA, a nitric oxide inhibitor. So far, the data has shown that the combination of GYS with L-NA causes less of a decrease in heartbeat frequency than GYS alone, which shows a significant decrease. We predict this is because GYS enhances the nitric oxide pathway, while L-NA is blocking the nitric oxide pathway, thus giving insight into the role of GYS within the lobster’s cardiac neuromuscular system. For my senior independent study I hope to continue this research and be able to continue to compile data for both SGRN and GYS on the isolated cardiac ganglion as well as on the whole heart, with a nitric oxide inhibitor and donor. Final Report of research funded by a Doherty Coastal Studies Research Fellowship.
Functional role of gamma and theta oscillations in episodic memory
Date: 2010-06-01
Creator: Erika Nyhus, Tim Curran
Access: Open access
- The primary aim of this review is to examine evidence for a functional role of gamma and theta oscillations in human episodic memory. It is proposed here that gamma and theta oscillations allow for the transient interaction between cortical structures and the hippocampus for the encoding and retrieval of episodic memories as described by the hippocampal memory indexing theory (Teyler and DiScenna, 1986). Gamma rhythms can act in the cortex to bind perceptual features and in the hippocampus to bind the rich perceptual and contextual information from diverse brain regions into episodic representations. Theta oscillations act to temporally order these individual episodic memory representations. Through feedback projections from the hippocampus to the cortex these gamma and theta patterns could cause the reinstatement of the entire episodic memory representation in the cortex. In addition, theta oscillations could allow for top-down control from the frontal cortex to the hippocampus modulating the encoding and retrieval of episodic memories. © 2009.
Components of the Springer fiber and domino tableaux
Date: 2004-02-15
Creator: Thomas Pietraho
Access: Open access
- Consider a complex classical semisimple Lie group along with the set of its nilpotent coadjoint orbits. When the group is of type A, the set of orbital varieties contained in a given nilpotent orbit is described a set of standard Young tableaux. We parameterize both, the orbital varieties and the irreducible components of unipotent varieties in the other classical groups by sets of standard domino tableaux. The main tools are Spaltenstein's results on signed domino tableaux together with Garfinkle's operations on standard domino tableaux. © 2004 Elsevier Inc. All rights reserved.
Carbon and hydrogen isotopic composition of methane over the last 1000 years
Date: 2009-10-01
Creator: J. A. Mischler, T. A. Sowers, R. B. Alley, M. Battle, J. R., McConnell, L. Mitchell, T. Popp, E. Sofen, M. K. Spencer
Access: Open access
- New measurements of the carbon and hydrogen isotopic ratios of methane (δ13 C of CH4 and δD of CH4) over the last millennium are presented from the WAIS Divide, Antarctica, ice core (WDC05A), showing significant changes that likely were the result of human influences prior to the industrial revolution (at least as early as the 16th century of the common era (CE)). The (δ13C of CH4 data corroborate the record from Law Dome, Antarctica, with high fidelity. The new δD of CH4 data set covaries with the (δ13C of CH4 record. Both (δ13C of CH4 and δD of CH4 were relatively stable and close to the present-day values from ∼to ∼CE. Both isotopic ratios decreased to minima around 1700 CE, remained low until the late 18th century, and then rose exponentially to present-day values. Our new δD of CH4 data provide an additional independent constraint for evaluating possible CH4 source histories. We searched a broad range of source scenarios using a simple box model to identify histories consistent with the constraints of the CH 4 concentration and isotope data from 990-1730 CE. Results typically show a decrease over time in the biomass-burning source (found in 85% of acceptable scenarios) and an increase in the agricultural source (found in 77% of acceptable scenarios), indicating preindustrial human influence on atmospheric methane as proposed in previous studies. © 2009 by the American Geophysical Union.