Showing 2011 - 2020 of 2040 Items
Circadian signaling in Homarus americanus: Region-specific de novo assembled transcriptomes show that both the brain and eyestalk ganglia possess the molecular components of a putative clock system
Date: 2018-07-01
Creator: Andrew E. Christie
Andy Yu
Micah G. Pascual
Vittoria Roncalli
Matthew C., Cieslak
Amanda N. Warner
Tess J. Lameyer
Meredith E. Stanhope
Patsy S. Dickinson
J. Joe Hull
Access: Open access
- Essentially all organisms exhibit recurring patterns of physiology/behavior that oscillate with a period of ~24-h and are synchronized to the solar day. Crustaceans are no exception, with robust circadian rhythms having been documented in many members of this arthropod subphylum. However, little is known about the molecular underpinnings of their circadian rhythmicity. Moreover, the location of the crustacean central clock has not been firmly established, although both the brain and eyestalk ganglia have been hypothesized as loci. The American lobster, Homarus americanus, is known to exhibit multiple circadian rhythms, and immunodetection data suggest that its central clock is located within the eyestalk ganglia rather than in the brain. Here, brain- and eyestalk ganglia-specific transcriptomes were generated and used to assess the presence/absence of transcripts encoding the commonly recognized protein components of arthropod circadian signaling systems in these two regions of the lobster central nervous system. Transcripts encoding putative homologs of the core clock proteins clock, cryptochrome 2, cycle, period and timeless were found in both the brain and eyestalk ganglia assemblies, as were transcripts encoding similar complements of putative clock-associated, clock input pathway and clock output pathway proteins. The presence and identity of transcripts encoding core clock proteins in both regions were confirmed using PCR. These findings suggest that both the brain and eyestalk ganglia possess all of the molecular components needed for the establishment of a circadian signaling system. Whether the brain and eyestalk clocks are independent of one another or represent a single timekeeping system remains to be determined. Interestingly, while most of the proteins deduced from the identified transcripts are shared by both the brain and eyestalk ganglia, assembly-specific isoforms were also identified, e.g., several period variants, suggesting the possibility of region-specific variation in clock function, especially if the brain and eyestalk clocks represent independent oscillators.
Inclusive and exclusive decays of B mesons to final states including charm and charmonium mesons
Date: 1992-01-01
Creator: D. Bortoletto
D. N. Brown
J. Dominick
R. L. McIlwain
D. H., Miller
M. Modesitt
E. I. Shibata
S. Schaffner
I. P.J. Shipsey
M. Battle
H. Kroha
K. Sparks
E. H. Thorndike
C. H. Wang
M. Goldberg
T. Haupt
N. Horwitz
V. Jain
G. C. Moneti
Y. Rozen
P. Rubin
T. Skwarnicki
V. Sharma
S. Stone
M. Thusalidas
W. M. Yao
G. Zhu
A. V. Barnes
J. Bartelt
S. E. Csorna
T. Letson
Access: Open access
- We have studied hadronic decays of B mesons. We report measurements of exclusive branching ratios of several charm decay modes of B mesons to final states with a D or D* and one to three charged pions or a charged and to final states with a or , a kaon, and up to two charged pions. We have also measured inclusive branching ratios for B decays to D and D* and the spectra of these particles in B decays. The total charm content in B decay is found to be (10112)%. The branching ratios and spectra are compared to form-factor models. We extract the parameters a1 and a2 of the model of Bauer, Stech, and Wirbel and the DS decay constant. The masses of the B0 and B- mesons are measured. The mass difference between B0 and B- is found to be -0.40.60.5 MeV/c2. © 1992 The American Physical Society.
Seeking shear waves in liquids with picosecond ultrasonics
Date: 2007-12-01
Creator: M. E. Msall
O. B. Wright
O. Matsuda
Access: Open access
- Picosecond shear acoustic pulses can be generated in solids using ultrashort optical pulses. Here we use this technique to seek high frequency shear waves in water, ethylene glycol and glycerol while simultaneously measuring high frequency longitudinal wave velocity and attenuation. We use a silica thin film on (114) GaAs to generate shear and longitudinal acoustic pulses at frequencies up to ∼50 GHz by ultrashort pulsed optical excitation. The acoustic pulses are transmitted into adjacent liquids, and are detected through variations in the optical reflectivity. Although we could not detect shear waves in these liquids, we did detect gigahertz longitudinal elastic stiffening. © 2007 IOP Publishing Ltd.
AMGSEFLamide, a member of a broadly conserved peptide family, modulates multiple neural networks in Homarus americanus
Date: 2019-01-01
Creator: Patsy S. Dickinson
Evyn S. Dickinson
Emily R. Oleisky
Cindy D. Rivera
Meredith E., Stanhope
Elizabeth A. Stemmler
J. Joe Hull
Andrew E. Christie
Access: Open access
- Recent genomic/transcriptomic studies have identified a novel peptide family whose members share the carboxyl terminal sequence –GSEFLamide. However, the presence/identity of the predicted isoforms of this peptide group have yet to be confirmed biochemically, and no physiological function has yet been ascribed to any member of this peptide family. To determine the extent to which GSEFLamides are conserved within the Arthropoda, we searched publicly accessible databases for genomic/transcriptomic evidence of their presence. GSEFLamides appear to be highly conserved within the Arthropoda, with the possible exception of the Insecta, in which sequence evidence was limited to the more basal orders. One crustacean in which GSEFLamides have been predicted using transcriptomics is the lobster, Homarus americanus. Expression of the previously published transcriptome-derived sequences was confirmed by reverse transcription (RT)-PCR of brain and eyestalk ganglia cDNAs; mass spectral analyses confirmed the presence of all six of the predicted GSEFLamide isoforms – IGSEFLamide, MGSEFLamide, AMGSEFLamide, VMGSEFLamide, ALGSEFLamide and AVGSEFLamide – in H. americanus brain extracts. AMGSEFLamide, of which there are multiple copies in the cloned transcripts, was the most abundant isoform detected in the brain. Because the GSEFLamides are present in the lobster nervous system, we hypothesized that they might function as neuromodulators, as is common for neuropeptides. We thus asked whether AMGSEFLamide modulates the rhythmic outputs of the cardiac ganglion and the stomatogastric ganglion. Physiological recordings showed that AMGSEFLamide potently modulates the motor patterns produced by both ganglia, suggesting that the GSEFLamides may serve as important and conserved modulators of rhythmic motor activity in arthropods.
TAKs, thylakoid membrane protein kinases associated with energy transduction
Date: 1999-04-02
Creator: Shaun Snyders
Bruce D. Kohorn
Access: Open access
- The phosphorylation of proteins within the eukaryotic photosynthetic membrane is thought to regulate a number of photosynthetic processes in land plants and algae. Both light quality and intensity influence protein kinase activity via the levels of reductants produced by the thylakoid electron transport chain. We have isolated a family of proteins called TAKs, Arabidopsis thylakoid membrane threonine kinases that phosphorylate the light harvesting complex proteins. TAK activity is enhanced by reductant and is associated with the photosynthetic reaction center II and the cytochrome b6f complex. TAKs are encoded by a gene family that has striking similarity to transforming growth factor β receptors of metazoans. Thus thylakoid protein phosphorylation may be regulated by a cascade of reductant-controlled membrane-bound protein kinases.
One-instanton predictions for non-hyperelliptic curves derived from M-theory
Date: 1998-12-21
Creator: Isabel P. Ennes
Stephen G. Naculich
Henric Rhedin
Howard J. Schnitzer
Access: Open access
- One-instanton predictions are obtained from certain non-hyperelliptic Seiberg-Witten curves derived from M-theory for N = 2 supersymmetric gauge theories. We consider SU(N1) × SU(N2) gauge theory with a hypermultiplet in the bifundamental representation together with hypermultiplets in the defining representations of SU(N1) and SU(N2). We also consider SU(N) gauge theory with a hypermultiplet in the symmetric or antisymmetric representation, together with hypermultiplets in the defining representation. The systematic perturbation expansion about a hyperelliptic curve together with the judicious use of an involution map for the curve of the product groups provide the principal tools of the calculations. © 1999 Elsevier Science B.V.
The 10kb Drosophila virus 28S rDNA intervening sequence is flanked by a disect repeat of 14 base pairs of coding sequence
Date: 1980-08-25
Creator: Peter M.M. Rae
Bruce D. Kohorn
Robert P. Wade
Access: Open access
- Most repeat units of rDNA in Drosophila virilis are interrupted in the 28S rRNA coding region by an intervening sequence about 10 kb in length; uninterrupted repeats have a length of about 11 kb. We have sequenced the coding/intervening sequence junctions and flanking regions in two independent clones of interrupted rDNA, and the corresponding 28S rRNA coding region in a clone of uninterrupted rDNA. The intervening sequence is terminated at both ends by a direct repeat of a fourteen nucleotide sequence that is present once in the corresponding region of an intact gene. This is a phenomenon associated with transposable elements in other eukaryotes and in prokaryotes, and the Drosophila rDNA intervening sequence is discussed in this context. We have compared more than 200 nucleotides of the D. virilis 28S rRNA gene with sequences of homologous regions of rDNA in Tetrahymena pigmentosa (Wild and Sommer, 1980) and Xenopus laevis (Gourse and Gerbi, 1980): There is 93% sequence homology among the diverse species, so that the rDNA region in question (about two-thirds of the way into the 28S rRNA coding sequence) has been very highly conserved in eukaryote evolution. The intervening sequence in T. pigmentosa is at a site 79 nucleotides upstream from the insertion site of the Drosophila intervening sequence. © 1980 IRL Press Limited.
Fermions destabilize electroweak strings
Date: 1995-01-01
Creator: Stephen G. Naculich
Access: Open access
- Z strings in the Weinberg-Salam model including fermions are unstable for all values of the parameters. The cause of this instability is the fermion vacuum energy in the Z-string background. Z strings with nonzero fermion densities, however, may still be stable. © 1995 The American Physical Society.
The supply of media slant across outlets and demand for slant within outlets: Evidence from US presidential campaign news
Date: 2020-06-01
Creator: Marcel Garz
Gaurav Sood
Daniel F. Stone
Justin Wallace
Access: Open access
- We conduct across-outlet and within-outlet (and within-topic) analyses of “congenially” slanted news. We study “horse race” news (news on candidates' chances in an upcoming election) from six major online outlets for the 2012 and 2016 US presidential campaigns. We find robust evidence that horse race headlines were slanted congenially with respect to the preferences of the outlets' typical readers. However, evidence of congenial slant in the timing and frequency of horse race stories is weaker. We also find limited evidence of greater within-outlet demand for headlines most congenial to outlets' typical readers, and somewhat stronger evidence of greater demand for relatively uncongenial headlines. We discuss how various aspects of our results are consistent with each of the major mechanisms driving slant studied in the theoretical literature, and may help explain when each mechanism is more likely to come into play. In particular, readers may be more likely to click on uncongenial headlines due to inferring that these stories are particularly informative when they stand in contrast to an outlet's typically congenial slant.
Monteverde: Ecology and Conservation of a Tropical Cloud Forest - 2014 Updated Chapters
Date: 2014-01-01
Creator: Nalini M Nadkarni
Nathaniel T Wheelwright
Access: Open access
- The Monteverde Cloud Forest Reserve has captured the worldwide attention of biologists, conservationists, and ecologists and has been the setting for extensive investigation over the past 40 years. Roughly 40,000 ecotourists visit the Cloud Forest each year, and it is often considered the archetypal high-altitude rain forest. “Monteverde: Ecology and Conservation of a Tropical Cloud Forest”, edited by Nalini Nadkarni and Nathaniel T. Wheelwright (Oxford University Press, 2000 and Bowdoin’s Scholar’s Bookshelf. Book 1 ), features synthetic chapters and specific accounts written by more than 100 biologist and local residents, presenting in a single volume everything known in 2000 about the biological diversity of Monteverde, Costa Rica, and how to protect it. The new short chapters written in 2014 by original contributors, and presented here update and expand that knowledge through 2014.