Showing 871 - 880 of 5701 Items
Three members of a peptide family are differentially distributed and elicit differential state-dependent responses in a pattern generator-effector system
Date: 2018-05-01
Creator: Patsy S. Dickinson, Matthew K. Armstrong, Evyn S. Dickinson, Rebecca Fernandez, Alexandra, Miller, Sovannarath Pong, Brian W. Powers, Alixander Pupo-Wiss, Meredith E. Stanhope, Patrick J. Walsh, Teerawat Wiwatpanit, Andrew E. Christie
Access: Open access
- C-type allatostatins (AST-Cs) are pleiotropic neuropeptides that are broadly conserved within arthropods; the presence of three AST-C isoforms, encoded by paralog genes, is common. However, these peptides are hypothesized to act through a single receptor, thereby exerting similar bioactivities within each species. We investigated this hypothesis in the American lobster, Homarus americanus, mapping the distributions of AST-C isoforms within relevant regions of the nervous system and digestive tract, and comparing their modulatory influences on the cardiac neuromuscular system. Immunohistochemistry showed that in the pericardial organ, a neuroendocrine release site, AST-C I and/or III and AST-C II are contained within distinct populations of release terminals. Moreover, AST-C I/III-like immunoreactivity was seen in midgut epithelial endocrine cells and the cardiac ganglion (CG), whereas AST-C II-like immunoreactivity was not seen in these tissues. These data suggest that AST-C I and/or III can modulate the CG both locally and hormonally; AST-C II likely acts on the CG solely as a hormonal modulator. Physiological studies demonstrated that all three AST-C isoforms can exert differential effects, including both increases and decreases, on contraction amplitude and frequency when perfused through the heart. However, in contrast to many state-dependent modulatory changes, the changes in contraction amplitude and frequency elicited by the AST-Cs were not functions of the baseline parameters. The responses to AST-C I and III, neither of which is COOH-terminally amidated, are more similar to one another than they are to the responses elicited by AST-C II, which is COOH-terminally amidated. These results suggest that the three AST-C isoforms are differentially distributed in the lobster nervous system/midgut and can elicit distinct behaviors from the cardiac neuromuscular system, with particular structural features, e.g., COOH-terminal amidation, likely important in determining the effects of the peptides. NEW & NOTEWORTHY Multiple isoforms of many peptides exert similar effects on neural circuits. In this study we show that each of the three isoforms of C-type allatostatin (AST-C) can exert differential effects, including both increases and decreases in contraction amplitude and frequency, on the lobster cardiac neuromuscular system. The distribution of effects elicited by the nonamidated isoforms AST-C I and III are more similar to one another than to the effects of the amidated AST-C II.
Investigating the role of eyes absent in photoreceptor axon targeting in Drosophila melanogaster
Date: 2021-01-01
Creator: Bethany J. Thach
Access: Open access
- The eya gene is essential to development of the Drosophila visual system and eye-specific loss of function mutations in the gene commonly result in the missing eye phenotype. The eya2m35g mutation carries a deletion of exon 1B and adjacent regulatory sequences. Flies carrying the eya2m35g allele exhibit a photoreceptor axon phenotype that has not previously been associated with the eya gene. To determine a potential role for eya in photoreceptor axon targeting, I characterized various phenotypes of eya2m35g mutants and generated additional eya alleles consisting of smaller deletions within the eya2m35g mutation to locate the genetic source of axonal disruption. Using immunofluorescence staining to visualize Eya protein, I found a loss of eya expression in the optic lobe region of eya2m35g stage 9 embryos and third instar larvae. I also observed a loss of retinal basal glial (RBG) cells in the larval eye disc. Finally, I demonstrated that the disconnected axon phenotype is generated when a region of the intron immediately downstream of exon 1B is deleted. These findings suggest that a possible regulatory element for eya that is essential for photoreceptor axon targeting exists in this intronic region.
Acute effects of sex steroids on visual processing in male goldfish
Date: 2018-01-01
Creator: S. Yue, V. Wadia, N. Sekula, P. S. Dickinson, R. R., Thompson
Access: Open access
- Elevations of sex steroids induced by social cues can rapidly modulate social behavior, but we know little about where they act within the nervous system to produce such effects. In male goldfish, testosterone (T) rapidly increases approach responses to the visual cues of females through its conversion to estradiol. Because aromatase is expressed in the retina, we tested if T can acutely influence retina responses to visual stimuli, and investigated the receptor mechanisms that may mediate such effects. Specifically, we measured FOS protein immunoreactivity to determine if T affects cellular responses to visual stimuli that include females, and used electrophysiology to investigate whether T can generally affect light sensitivity. We found that T acutely increased FOS responses to the simultaneous onset of light and the presence of female visual stimuli, both of which would normally be associated with early morning spawning, and increased electrophysiological responses to low intensity light pulses. Both effects were blocked by an estrogen receptor beta (ERβ) antagonist, indicating that T is likely being converted to estradiol (E2) and acting through an ERβ mediated mechanism to acutely modulate visual processing. Changes in sensory processing could subsequently influence approach behavior to increase reproductive success in competitive mating environments.
Prediction of a neuropeptidome for the eyestalk ganglia of the lobster Homarus americanus using a tissue-specific de novo assembled transcriptome
Date: 2017-03-01
Creator: Andrew E. Christie, Vittoria Roncalli, Matthew C. Cieslak, Micah G. Pascual, Andy, Yu, Tess J. Lameyer, Meredith E. Stanhope, Patsy S. Dickinson
Access: Open access
- In silico transcriptome mining is a powerful tool for crustacean peptidome prediction. Using homology-based BLAST searches and a simple bioinformatics workflow, large peptidomes have recently been predicted for a variety of crustaceans, including the lobster, Homarus americanus. Interestingly, no in silico studies have been conducted on the eyestalk ganglia (lamina ganglionaris, medulla externa, medulla interna and medulla terminalis) of the lobster, although the eyestalk is the location of a major neuroendocrine complex, i.e., the X-organ-sinus gland system. Here, an H. americanus eyestalk ganglia-specific transcriptome was produced using the de novo assembler Trinity. This transcriptome was generated from 130,973,220 Illumina reads and consists of 147,542 unique contigs. Eighty-nine neuropeptide-encoding transcripts were identified from this dataset, allowing for the deduction of 62 distinct pre/preprohormones. Two hundred sixty-two neuropeptides were predicted from this set of precursors; the peptides include members of the adipokinetic hormone-corazonin-like peptide, allatostatin A, allatostatin B, allatostatin C, bursicon α, CCHamide, corazonin, crustacean cardioactive peptide, crustacean hyperglycemic hormone (CHH), CHH precursor-related peptide, diuretic hormone 31, diuretic hormone 44, eclosion hormone, elevenin, FMRFamide-like peptide, glycoprotein hormone α2, glycoprotein hormone β5, GSEFLamide, intocin, leucokinin, molt-inhibiting hormone, myosuppressin, neuroparsin, neuropeptide F, orcokinin, orcomyotropin, pigment dispersing hormone, proctolin, pyrokinin, red pigment concentrating hormone, RYamide, short neuropeptide F, SIFamide, sulfakinin, tachykinin-related peptide and trissin families. The predicted peptides expand the H. americanus eyestalk ganglia neuropeptidome approximately 7-fold, and include 78 peptides new to the lobster. The transcriptome and predicted neuropeptidome described here provide new resources for investigating peptidergic signaling within/from the lobster eyestalk ganglia.
Wave transmission in time- and space-variant helicoidal phononic crystals
Date: 2014-11-04
Creator: F. Li, C. Chong, J. Yang, P. G. Kevrekidis, C., Daraio
Access: Open access
- We present a dynamically tunable mechanism of wave transmission in one-dimensional helicoidal phononic crystals in a shape similar to DNA structures. These helicoidal architectures allow slanted nonlinear contact among cylindrical constituents, and the relative torsional movements can dynamically tune the contact stiffness between neighboring cylinders. This results in cross-talking between in-plane torsional and out-of-plane longitudinal waves. We numerically demonstrate their versatile wave mixing and controllable dispersion behavior in both wavenumber and frequency domains. Based on this principle, a suggestion toward an acoustic configuration bearing parallels to a transistor is further proposed, in which longitudinal waves can be switched on and off through torsional waves.
Midterm Decline in Comparative Perspective
Date: 2019-05-01
Creator: Duncan Gans
Access: Open access
Lesley Vance
Date: 2011-01-01
Creator: Diana K. Tuite
Access: Open access
- Catalog of an exhibition held April 12-July 1, 2012, at the Bowdoin College Museum of Art, Brunswick, Maine. Includes essay "Conspiring forms" by Diana Tuite (p. 2-3)
The Jewish “Other” in Argentina: Antisemitism, Exclusion, and the Formation of Argentine Nationalism and Identity in the 20th Century and during Military Rule (1976-1983)
Date: 2021-01-01
Creator: Marcus Helble
Access: Open access
- Throughout the 20th century, Argentine leaders and social actors attempted to shape distinct national identities and a sense of nationalism that corresponded to their respective political ideologies. Beginning in the first couple decades of the 20th century, the formation of a Jewish “other” would be central to the construction of both Argentine national identity and nationalism. This thesis argues that the military dictatorship that led the country from 1976 to 1983 built on this othering of the Jewish community as military leaders sought to forge a national identity linked to Catholicism. It focuses first on three separate periods of the early and mid-20th centuries and how governments in that period built, maintained, and altered the view of the Jewish community as a not fully Argentine “other” living in the country. Using several editions of a far-right antisemitic periodical, declassified State Department documents, and testimonies of Jewish political prisoners and soldiers, the thesis transitions to focus on the military dictatorship of the 1970s and 1980s. It examines two separate periods of the dictatorship, highlighting first the role antisemitic beliefs, and opposing such views, had in an internal power struggle within the military government. In the second period of the dictatorship, during the Malvinas (Falklands) War, the thesis examines how antisemitism became a central part of the military’s efforts to consolidate a sense of national unity during the conflict, even as Jews participated largely for the first time within Argentine nationalism and the military.
The peptide hormone pQDLDHVFLRFamide (crustacean myosuppressin) modulates the Homarus americanus cardiac neuromuscular system at multiple sites
Date: 2009-12-15
Creator: J. S. Stevens, C. R. Cashman, C. M. Smith, K. M. Beale, D. W., Towle, A. E. Christie, P. S. Dickinson
Access: Open access
- pQDLDHVFLRFamide is a highly conserved crustacean neuropeptide with a structure that places it within the myosuppressin subfamily of the FMRFamide-like peptides. Despite its apparent ubiquitous conservation in decapod crustaceans, the paracrine and/or endocrine roles played by pQDLDHVFLRFamide remain largely unknown. We have examined the actions of this peptide on the cardiac neuromuscular system of the American lobster Homarus americanus using four preparations: the intact animal, the heart in vitro, the isolated cardiac ganglion (CG), and a stimulated heart muscle preparation. In the intact animal, injection of myosuppressin caused a decrease in heartbeat frequency. Perfusion of the in vitro heart with pQDLDHVFLRFamide elicited a decrease in the frequency and an increase in the amplitude of heart contractions. In the isolated CG, myosuppressin induced a hyperpolarization of the resting membrane potential of cardiac motor neurons and a decrease in the cycle frequency of their bursting. In the stimulated heart muscle preparation, pQDLDHVFLRFamide increased the amplitude of the induced contractions, suggesting that myosuppressin modulates not only the CG, but also peripheral sites. For at least the in vitro heart and the isolated CG, the effects of myosuppressin were dose-dependent (10 -9 to 10-6mol l-1 tested), with threshold concentrations (10-8-10-7 mol l-1) consistent with the peptide serving as a circulating hormone. Although cycle frequency, a parameter directly determined by the CG, consistently decreased when pQDLDHVFLRFamide was applied to all preparation types, the magnitudes of this decrease differed, suggesting the possibility that, because myosuppressin modulates the CG and the periphery, it also alters peripheral feedback to the CG.