Showing 801 - 810 of 2040 Items
The moment of inertia of the binary pulsar J0737-3039A: Constraining the nuclear equation of state
Date: 2004-01-01
Creator: I.A. Morrison
T.W. Baumgarte
S.L. Shapiro
V.R. Pandharipande
Access: Open access
Molecular, mass spectral, and physiological analyses of orcokinins and orcokinin precursor-related peptides in the lobster Homarus americanus and the crayfish Procambarus clarkii
Date: 2009-02-01
Creator: Patsy S. Dickinson
Elizabeth A. Stemmler
Elizabeth E. Barton
Christopher R. Cashman
Noah P., Gardner
Szymon Rus
Henry R. Brennan
Timothy S. McClintock
Andrew E. Christie
Access: Open access
- Recently, cDNAs encoding prepro-orcokinins were cloned from the crayfish Procambarus clarkii; these cDNAs encode multiple copies of four orcokinin isoforms as well as several other peptides. Using the translated open reading frames of the P. clarkii transcripts as queries, five ESTs encoding American lobster Homarus americanus orthologs were identified via BLAST analysis. From these clones, three cDNAs, each encoding one of two distinct prepro-hormones, were characterized. Predicted processing of the deduced prepro-hormones would generate 13 peptides, 12 of which are conserved between the 2 precursors: the orcokinins NFDEIDRSGFGFN (3 copies), NFDEIDRSGFGFH (2 copies) and NFDEIDRSGFGFV (2 copies), FDAFTTGFGHN (an orcomyotropin-related peptide), SSEDMDRLGFGFN, GDY(SO3)DVYPE, VYGPRDIANLY and SAE. Additionally, one of two longer peptides (GPIKVRFLSAIFIPIAAPARSSPQQDAAAGYTDGAPV or APARSSPQQDAAAGYTDGAPV) is predicted from each prepro-hormone. MALDI-FTMS analyses confirmed the presence of all predicted orcokinins, the orcomyotropin-related peptide, and three precursor-related peptides, SSEDMDRLGFGFN, GDYDVYPE (unsulfated) and VYGPRDIANLY, in H. americanus neural tissues. SAE and the longer, unshared peptides were not detected. Similar complements of peptides are predicted from P. clarkii transcripts; the majority of these were detected in its neural tissues with mass spectrometry. Truncated orcokinins not predicted from any precursor were also detected in both species. Consistent with previous studies in the crayfish Orconectes limosus, NFDEIDRSGFGFN increased mid-/hindgut motility in P. clarkii. Surprisingly, the same peptide, although native to H. americanus, did not affect gut motility in this species. Together, our results provide the framework for future investigations of the regulation and physiological function of orcokinins/orcokinin precursor-related peptides in astacideans. © 2008 Elsevier Inc. All rights reserved.
Effect of differential rotation on the maximum mass of neutron stars: Realistic nuclear equations of state
Date: 2004-01-01
Creator: I.A. Morrison
T.W. Baumgarte
S.L. Shapiro
Access: Open access
General relativistic magnetohydrodynamics for the numerical construction of dynamical spacetimes
Date: 2003-01-01
Creator: T.W. Baumgarte
S.L. Shapiro
Access: Open access
Midgut epithelial endocrine cells are a rich source of the neuropeptides APSGFLGMRamide (Cancer borealis tachykinin-related peptide Ia) and GYRKPPFNGSIFamide (Gly1-SIFamide) in the crabs Cancer borealis, Cancer magister and Cancer productus
Date: 2007-02-01
Creator: Andrew E. Christie
Kimberly K. Kutz-Naber
Elizabeth A. Stemmler
Alexandra Klein
Daniel I., Messinger
Christopher C. Goiney
Anna J. Conterato
Emily A. Bruns
Yun Wei A. Hsu
Lingjun Li
Patsy S. Dickinson
Access: Open access
- Over a quarter of a century ago, Mykles described the presence of putative endocrine cells in the midgut epithelium of the crab Cancer magister (Mykles, 1979). In the years that have followed, these cells have been largely ignored and nothing is known about their hormone content or the functions they play in this species. Here, we used a combination of immunohistochemistry and mass spectrometric techniques to investigate these questions. Using immunohistochemistry, we identified both SIFamide-and tachykinin-related peptide (TRP)-like immunopositive cells in the midgut epithelium of C. magister, as well as in that of Cancer borealis and Cancer productus. In each species, the SIFamide-like labeling was restricted to the anterior portion of the midgut, including the paired anterior midgut caeca, whereas the TRP-like immunoreactivity predominated in the posterior midgut and the posterior midgut caecum. Regardless of location, label or species, the morphology of the immunopositive cells matched that of the putative endocrine cells characterized ultrastructurally by Mykles (Mykles, 1979). Matrix-assisted laser desorption/ ionization-Fourier transform mass spectrometry identified the peptides responsible for the immunoreactivities as GYRKPPFNGSIFamide (Gly 1-SIFamide) and APSGFLGMRamide [Cancer boreatis tachykinin-related peptide Ia (CabTRP Ia)], respectively, both of which are known neuropeptides of Cancer species. Although the function of these midgut-derived peptides remains unknown, we found that both Gly1-SIFamide and CabTRP Ia were released when the midgut was exposed to high-potassium saline. In addition, CabTRP Ia was detectable in the hemolymph of crabs that had been held without food for several days, but not in that of fed animals, paralleling results that were attributed to TRP release from midgut endocrine cells in insects. Thus, one function that midgut-derived CabTRP Ia may play in Cancer species is paracrine/hormonal control of feeding-related behavior, as has been postulated for TRPs released from homologous cells in insects.
Neurotransmitter interactions in the stomatogastric system of the spiny lobster: One peptide alters the response of a central pattern generator to a second peptide
Date: 1997-01-01
Creator: Patsy S. Dickinson
Wesley P. Fairfield
John R. Hetling
Jane Hauptman
Access: Open access
- Two of the peptides found in the stomatogastric nervous system of the spiny lobster. Panulirus interruptus, interacted to modulate the activity of the cardiac sac motor pattern. In the isolated stomatogastric ganglion, red- pigment-concentrating hormone (RPCH), but not proctolin, activated the bursting activity in the inferior ventricular (IV) neurons that drives the cardiac sac pattern. The cardiac sac pattern normally ceased within 15 min after the end of RPCH superfusion. However, when proctolin was applied within a few minutes of that time, it was likewise able to induce cardiac sac activity. Similarly, proctolin applied together with subthreshold RPCH induced cardiac sac bursting. The amplitude of the excitatory postsynaptic potentials from the IV neurons to the cardiac sac dilator neuron CD2 (1 of the 2 major motor neurons in the cardiac sac system) was potentiated in the presence of both proctolin and RPCH. The potentiation in RPCH was much greater than in proctolin alone. However, the potentiation in proctolin after RPCH was equivalent to that recorded in RPCH alone. Although we do not yet understand the mechanisms for these interactions of the two modulators, this study provides an example of one factor that can determine the 'state' of the system that is critical in determining the effect of a modulator that is 'state dependent,' and it provides evidence for yet another level of flexibility in the motor output of this system.
Focusing Surface-Acoustic-Wave Microcavities on GaAs
Date: 2020-01-22
Creator: Madeleine E. Msall
Paulo V. Santos
Access: Open access
- Focusing microcavities for surface acoustic waves (SAWs) produce highly localized strain and piezoelectric fields that can dynamically control excitations in nanostructures. Focusing transducers (FIDTs) that generate SAW beams that match nanostructure dimensions require pattern correction due to diffraction and wave-velocity anisotropy. The anisotropy correction is normally implemented by adding a quadratic term to the dependence of the wave velocity on the propagation angle. We show that a SAW focusing to a diffraction-limited size in GaAs requires corrections that more closely follow the group-velocity wave front, which is not a quadratic function. Optical interferometric mapping of the resultant SAW displacement field reveals tightly focused SAW beams on GaAs with a minimal beam waist. An additional set of Gouy-phase-corrected passive fingers creates an acoustic microcavity in the focal region with a small volume and a high quality factor. Our λSAW=5.6μm FIDTs are expected to scale well to the approximately 500-nm wavelength regime needed to study strong coupling between vibrations and electrons in electrostatic GaAs quantum dots.
Targeted identification of glycosylated proteins in the gastric pathogen helicobacter pylori (Hp)
Date: 2013-09-01
Creator: Kanokwan Champasa
Scott A. Longwell
Aimee M. Eldridge
Elizabeth A. Stemmler
Danielle H., Dube
Access: Open access
- Virulence of the gastric pathogen Helicobacter pylori (Hp) is directly linked to the pathogen's ability to glycosylate proteins; for example, Hp flagellin proteins are heavily glycosylated with the unusual nine-carbon sugar pseudaminic acid, and this modification is absolutely essential for Hp to synthesize functional flagella and colonize the host's stomach. Although Hp's glycans are linked to pathogenesis, Hp's glycome remains poorly understood; only the two flagellin glycoproteins have been firmly characterized in Hp. Evidence from our laboratory suggests that Hp synthesizes a large number of as-yet unidentified glycoproteins. Here we set out to discover Hp's glycoproteins by coupling glycan metabolic labeling with mass spectrometry analysis. An assessment of the subcellular distribution of azide-labeled proteins by Western blot analysis indicated that glycoproteins are present throughout Hp and may therefore serve diverse functions. To identify these species, Hp's azide-labeled glycoproteins were tagged via Staudinger ligation, enriched by tandem affinity chromatography, and analyzed by multidimensional protein identification technology. Direct comparison of enriched azide-labeled glycoproteins with a mock-enriched control by both SDS-PAGE and mass spectrometry-based analyses confirmed the selective enrichment of azide-labeled glycoproteins. We identified 125 candidate glycoproteins with diverse biological functions, including those linked with pathogenesis. Mass spectrometry analyses of enriched azide-labeled glycoproteins before and after cleavage of O-linked glycans revealed the presence of Staudinger ligation-glycan adducts in samples only after beta-elimination, confirming the synthesis of O-linked glycoproteins in Hp. Finally, the secreted colonization factors urease alpha and urease beta were biochemically validated as glycosylated proteins via Western blot analysis as well as by mass spectrometry analysis of cleaved glycan products. These data set the stage for the development of glycosylation-based therapeutic strategies, such as new vaccines based on natively glycosylated Hp proteins, to eradicate Hp infection. Broadly, this report validates metabolic labeling as an effective and efficient approach for the identification of bacterial glycoproteins. © 2013 by The American Society for Biochemistry and Molecular Biology, Inc.
Reconsidering Operation Condor: Cross-border Military Cooperation and the Defeat of the Transnational Left in Chile and Argentina during the 1970s
Date: 2014-05-01
Creator: Georgia C Whitaker
Access: Open access
- In this study of the roots of Operation Condor, I track the development of this unusual military alliance forged by six Southern Cone governments (Chile, Argentina, Brazil, Bolivia, Uruguay, and Paraguay) during the 1970s, as well as the push-and-pull relationship between the transnational migration of political militants and the military’s impetus for collaboration. While most accounts of Condor focus on the United States as the operation’s primary orchestrator, I contend that initial motivation for the type of cooperation that Condor would later formalize was driven not by the U.S., but by the Southern Cone militaries’ perception that Marxism had to be excised from the entire region. In addition, while Condor scholars have either ignored or minimized the role of the left as political actors and placed the blame for violence exclusively on the militaries and the United States, I draw from unpublished Argentine police records, Argentine Embassy documents, and Chilean-Argentine solidarity group publications to argue that it is essential to broaden our understanding of what both sides in this ideological confrontation were attempting to accomplish. The transnational left, never a homogenous group, evolved to meet a variety of objectives. Many militants continued to be politically active while they were in exile, and many acted in solidarity with like-minded leftists in their midst.
Digital Authoritarianism in China and Russia: A Comparative Study
Date: 2020-01-01
Creator: Laura H.C. Howells
Access: Open access
- Digital authoritarianism is on the rise around the world and threatens the data privacy and rights of both domestic and international Internet users. However, scholarship on digital authoritarianism remains limited in scope and case study selection. This study contributes a new, more comprehensive analytical framework for the study of Internet governance and applies it to the case studies of China and Russia. Special attention is paid to the still understudied Russian Internet governance model. After thorough literature review and novel data collection and analysis, this paper identifies relative centralization of network infrastructure and the extent and pace of change in governance as the most notable differences between the two models. These points of divergence may be explained by two theories; the varieties of authoritarianism hypothesis posits that different political systems face persistent and unique constraints to governance of the digital realm. The development trajectory theory argues that each country’s technological development path foreshadows the systems’ capacity for and extent of governance. This study is among the first to distinguish between Internet governance strategies of authoritarian regimes.