Showing 181 - 190 of 2040 Items
Statement by Alivia Moore collected by Heather Westleigh on November 4, 2014
Date: 2014-11-04
Creator: Alivia Moore
Access: Open access
Statement by Lucille Atwell collected by Rachel george on June 25, 2014
Date: 2014-06-25
Creator: Lucille Atwell
Access: Open access
Statement by Mikhu Paul collected by Rachel George on December 18, 2014
Date: 2014-12-18
Creator: Mikhu Paul
Access: Open access
Fgf signaling is required for zebrafish tooth development
Date: 2004-10-01
Creator: William R. Jackman
Bruce W. Draper
David W. Stock
Access: Open access
- We have investigated fibroblast growth factor (FGF) signaling during the development of the zebrafish pharyngeal dentition with the goal of uncovering novel roles for FGFs in tooth development as well as phylogenetic and topographic diversity in the tooth developmental pathway. We found that the tooth-related expression of several zebrafish genes is similar to that of their mouse orthologs, including both epithelial and mesenchymal markers. Additionally, significant differences in gene expression between zebrafish and mouse teeth are indicated by the apparent lack of fgf8 and pax9 expression in zebrafish tooth germs. FGF receptor inhibition with SU5402 at 32 h blocked dental epithelial morphogenesis and tooth mineralization. While the pharyngeal epithelium remained intact as judged by normal pitx2 expression, not only was the mesenchymal expression of lhx6 and lhx7 eliminated as expected from mouse studies, but the epithelial expression of dlx2a, dlx2b, fgf3, and fgf4 was as well. This latter result provides novel evidence that the dental epithelium is a target of FGF signaling. However, the failure of SU5402 to block localized expression of pitx2 suggests that the earliest steps of tooth initiation are FGF-independent. Investigations of specific FGF ligands with morpholino antisense oligonucleotides revealed only a mild tooth shape phenotype following fgf4 knockdown, while fgf8 inhibition revealed only a subtle down-regulation of dental dlx2b expression with no apparent effect on tooth morphology. Our results suggest redundant FGF signals target the dental epithelium and together are required for dental morphogenesis. Further work will be required to elucidate the nature of these signals, particularly with respect to their origins and whether they act through the mesenchyme. © 2004 Elsevier Inc. All rights reserved.
The 'obligate diploid' Candida albicans forms mating-competent haploids
Date: 2013-02-07
Creator: Meleah A. Hickman
Guisheng Zeng
Anja Forche
Matthew P. Hirakawa
Darren, Abbey
Benjamin D. Harrison
Yan Ming Wang
Ching Hua Su
Richard J. Bennett
Yue Wang
Judith Berman
Access: Open access
- Candida albicans, the most prevalent human fungal pathogen, is considered to be an obligate diploid that carries recessive lethal mutations throughout the genome. Here we demonstrate that C. albicans has a viable haploid state that can be derived from diploid cells under in vitro and in vivo conditions, and that seems to arise through a concerted chromosome loss mechanism. Haploids undergo morphogenetic changes like those of diploids, including the yeast-hyphal transition, chlamydospore formation and a white-opaque switch that facilitates mating. Haploid opaque cells of opposite mating type mate efficiently to regenerate the diploid form, restoring heterozygosity and fitness. Homozygous diploids arise spontaneously by auto-diploidization, and both haploids and auto-diploids show a similar reduction in fitness, in vitro and in vivo, relative to heterozygous diploids, indicating that homozygous cell types are transient in mixed populations. Finally, we constructed stable haploid strains with multiple auxotrophies that will facilitate molecular and genetic analyses of this important pathogen. © 2013 Macmillan Publishers Limited. All rights reserved.
Global divergence of the human follicle mite Demodex folliculorum: Persistent associations between host ancestry and mite lineages
Date: 2015-12-29
Creator: Michael F. Palopoli
Daniel J. Fergus
Samuel Minot
Dorothy T. Pei
W. Brian, Simison
Iria Fernandez-Silva
Megan S. Thoemmes
Robert R. Dunn
Michelle Trautwein
Access: Open access
- Microscopic mites of the genus Demodex live within the hair follicles of mammals and are ubiquitous symbionts of humans, but little molecular work has been done to understand their genetic diversity or transmission. Here we sampled mite DNA from 70 human hosts of diverse geographic ancestries and analyzed 241 sequences from the mitochondrial genome of the species Demodex folliculorum. Phylogenetic analyses recovered multiple deep lineages including a globally distributed lineage common among hosts of European ancestry and three lineages that primarily include hosts of Asian, African, and Latin American ancestry. To a great extent, the ancestral geography of hosts predicted the lineages of mites found on them; 27% of the total molecular variance segregated according to the regional ancestries of hosts. We found that D. folliculorum populations are stable on an individual over the course of years and that some Asian and African American hosts maintain specific mite lineages over the course of years or generations outside their geographic region of birth or ancestry. D. folliculorum haplotypes were much more likely to be shared within families and between spouses than between unrelated individuals, indicating that transmission requires close contact. Dating analyses indicated that D. folliculorum origins may predate modern humans. Overall, D. folliculorum evolution reflects ancient human population divergences, is consistent with an out-of-Africa dispersal hypothesis, and presents an excellent model system for further understanding the history of human movement.
Religion and science in the Eastern mediterranean
Date: 2016-09-01
Creator: Robert Morrison
Access: Open access
- “Science and Orthodox Christianity: An Overview” is an ambitious survey that reminds scholars of science in Islamic societies that the conversation between Islam and science is really a conversation between Islam and science in different contexts and that conversations between Islam and science can be found with less renowned scientific developments such as prophetic medicine. This response points out parallels in how Greek Orthodox and Ottoman Muslim scholars mediated new developments in Western European science and in how both Greek Orthodox and some Ottoman Muslim scholars propounded a mathematical humanism. Finally, it argues that the account of post-1453 scientific exchange is more complex than “Science and Orthodox Christianity” intimates. At the least, if there was no scholarly exchange between Greek Orthodox Christians, on the one hand, and, on the other hand, Muslims and Jews—who, in turn, enjoyed scholarly exchange with the West well after 1453—there are clearly two different Easts.
Civil Society under the Law ‘On Foreign Agents’: NGO Strategies and Network Transformation
Date: 2018-04-21
Creator: Maria Tysiachniouk
Svetlana Tulaeva
Laura A. Henry
Access: Open access
- This essay analyses how the ‘foreign agent’ law has been interpreted and implemented by the Russian authorities and examines diverse NGO survival strategies in response to the ‘foreign agent’ label. The foreign agent law has disrupted and transformed resource mobilisation strategies and transnational NGO networks. Based on qualitative research on environmental NGOs, we offer a typology of NGO responses to the foreign agent law, providing examples to show how the organisations attempt to ensure their survival.
The initiation and development of small peat-forming ecosystems adjacent to lakes in the north central Canadian low arctic during the Holocene
Date: 2017-07-01
Creator: Philip Camill
Charles E. Umbanhowar
Christoph Geiss
Mark B. Edlund
Will O., Hobbs
Allison Dupont
Catherine Doyle-Capitman
Matthew Ramos
Access: Open access
- Small peat-forming ecosystems in arctic landscapes may play a significant role in the regional biogeochemistry of high-latitude systems, yet they are understudied compared to arctic uplands and other major peat-forming regions of the North. We present a new data set of 25 radiocarbon-dated permafrost peat cores sampled around eight low arctic lake sites in northern Manitoba (Canada) to examine the timing of peat initiation and controls on peat accumulation throughout the Holocene. We used macrofossils and charcoal to characterize changes in the plant community and fire, and we explored potential impacts of these local factors, as well as regional climatic change, on rates of C accumulation and C stocks. Peat initiation was variable across and within sites, suggesting the influence of local topography, but 56% of the cores initiated after 3000 B.P. Most cores initiated and remained as drier bog hummock communities, with few vegetation transitions in this landscape. C accumulation was relatively slow and did not appear to be correlated with Holocene-scale climatic variability, but C stocks in this landscape were substantial (mean = 45.4 kg C m ), potentially accounting for 13.2 Pg C in the Taiga Shield ecozone. To the extent that small peat-forming systems are underrepresented in peatland mapping, soil organic carbon (SOC) stocks may be underestimated in arctic regions. Mean fire severity appeared to be negatively correlated with C accumulation rates. Initiation and accumulation of soil C may respond to both regional and local factors, and substantial lowland soil C stocks have the potential for biogeochemical impacts on adjacent aquatic ecosystems. −2
Conical wave propagation and diffraction in two-dimensional hexagonally packed granular lattices
Date: 2016-01-25
Creator: C. Chong
P. G. Kevrekidis
M. J. Ablowitz
Yi Ping Ma
Access: Open access
- Linear and nonlinear mechanisms for conical wave propagation in two-dimensional lattices are explored in the realm of phononic crystals. As a prototypical example, a statically compressed granular lattice of spherical particles arranged in a hexagonal packing configuration is analyzed. Upon identifying the dispersion relation of the underlying linear problem, the resulting diffraction properties are considered. Analysis both via a heuristic argument for the linear propagation of a wave packet and via asymptotic analysis leading to the derivation of a Dirac system suggests the occurrence of conical diffraction. This analysis is valid for strong precompression, i.e., near the linear regime. For weak precompression, conical wave propagation is still possible, but the resulting expanding circular wave front is of a nonoscillatory nature, resulting from the complex interplay among the discreteness, nonlinearity, and geometry of the packing. The transition between these two types of propagation is explored.