Showing 201 - 210 of 257 Items
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.
C-terminal methylation of truncated neuropeptides: An enzyme- assistedextraction artifact involving methanol
Date: 2013-01-01
Creator: Elizabeth A. Stemmler, Elizabeth E. Barton, Onyinyechi K. Esonu, Daniel A. Polasky, Laura L., Onderko, Audrey B. Bergeron, Andrew E. Christie, Patsy S. Dickinson
Access: Open access
- Neuropeptides are the largest class of signaling molecules used by nervous systems. Today, neuropeptidediscovery commonly involves chemical extraction from a tissue source followed by mass spectrometriccharacterization. Ideally, the extraction procedure accurately preserves the sequence and any inher-ent modifications of the native peptides. Here, we present data showing that this is not always true.Specifically, we present evidence showing that, in the lobster Homarus americanus, the orcokinin fam-ily members, NFDEIDRSGFG-OMe and SSEDMDRLGFG-OMe, are non-native peptides generated fromfull-length orcokinin precursors as the result of a highly selective peptide modification (peptide trun-cation with C-terminal methylation) that occurs during extraction. These peptides were observed byMALDI-FTMS and LC-Q-TOFMS analyses when eyestalk ganglia were extracted in a methanolic solvent,but not when tissues were dissected, co-crystallized with matrix, and analyzed directly with methanolexcluded from the sample preparation. The identity of NFDEIDRSGFG-OMe was established using MALDI-FTMS/SORI-CID, LC-Q-TOFMS/MS, and comparison with a peptide standard. Extraction substitutingdeuterated methanol for methanol confirmed that the latter is the source of the C-terminal methyl group,and MS/MS confirmed the C-terminal localization of the added CD3. Surprisingly, NFDEIDRSGFG-OMe isnot produced via a chemical acid-catalyzed esterification. Instead, the methylated peptide appears toresult from proteolytic truncation in the presence of methanol, as evidenced by a reduction in conver-sion with the addition of a protease-inhibitor cocktail; heat effectively eliminated the conversion. Thisunusual and highly specific extraction-derived peptide conversion exemplifies the need to consider bothchemical and biochemical processes that may modify the structure of endogenous neuropeptides. © 2013 The Authors. Published by Elsevier Inc. All rights reserved.
The quantitative genetics of incipient speciation: Heritability and genetic correlations of skeletal traits in populations of diverging favia fragum ecomorphs
Date: 2011-12-01
Creator: David B. Carlon, Ann F. Budd, Catherine Lippé, Rose L. Andrew
Access: Open access
- Recent speciation events provide potential opportunities to understand the microevolution of reproductive isolation. We used a marker-based approach and a common garden to estimate the additive genetic variation in skeletal traits in a system of two ecomorphs within the coral species Favia fragum: a Tall ecomorph that is a seagrass specialist, and a Short ecomorph that is most abundant on coral reefs. Considering both ecomorphs, we found significant narrow-sense heritability (h 2) in a suite of measurements that define corallite architecture, and could partition additive and nonadditive variation for some traits. We found positive genetic correlations for homologous height and length measurements among different types of vertical plates (costosepta) within corallites, but negative correlations between height and length within, as well as between costosepta. Within ecomorphs, h 2 estimates were generally lower, compared to the combined ecomorph analysis. Marker-based estimates of h 2 were comparable to broad-sense heritability (H) obtained from parent-offspring regressions in a common garden for most traits, and similar genetic co-variance matrices for common garden and wild populations may indicate relatively small G × E interactions. The patterns of additive genetic variation in this system invite hypotheses of divergent selection or genetic drift as potential evolutionary drivers of reproductive isolation. © 2011 The Author(s). Evolution© 2011 The Society for the Study of Evolution.
The neuromuscular transform of the lobster cardiac system explains the opposing effects of a neuromodulator on muscle output
Date: 2013-10-18
Creator: Alex H. Williams, Andrew Calkins, Timothy O'Leary, Renee Symonds, Eve, Marder, Patsy S. Dickinson
Access: Open access
- Motor neuron activity is transformed into muscle movement through a cascade of complex molecular and biomechanical events. This nonlinear mapping of neural inputs to motor behaviors is called the neuromuscular transform (NMT). We examined the NMT in the cardiac system of the lobster Homarus americanus by stimulating a cardiac motor nerve with rhythmic bursts of action potentials and measuring muscle movements in response to different stimulation patterns. The NMT was similar across preparations, which suggested that it could be used to predict muscle movement from spontaneous neural activity in the intact heart. We assessed this possibility across semi-intact heart preparations in two separate analyses. First, we performed a linear regression analysis across 122 preparations in physiological saline to predict muscle movements from neural activity. Under these conditions, the NMT was predictive of contraction duty cycle but was unable to predict contraction amplitude, likely as a result of uncontrolled interanimal variability. Second, we assessed the ability of the NMT to predict changes in motor output induced by the neuropeptide C-type allatostatin. Wiwatpanit et al. (2012) showed that bath application of C-type allatostatin produced either increases or decreases in the amplitude of the lobster heart contractions. We show that an important component of these preparation-dependent effects can arise from quantifiable differences in the basal state of each preparation and the nonlinear form of the NMT. These results illustrate how properly characterizing the relationships between neural activity and measurable physiological outputs can provide insight into seemingly idiosyncratic effects of neuromodulators across individuals. © 2013 the authors.
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.
Identification, physiological actions, and distribution of TPSGFLGMRamide: A novel tachykinin-related peptide from the midgut and stomatogastric nervous system of Cancer crabs
Date: 2007-06-01
Creator: Elizabeth A. Stemmler, Braulio Peguero, Emily A. Bruns, Patsy S. Dickinson, Andrew E., Christie
Access: Open access
- In most invertebrates, multiple species-specific isoforms of tachykinin-related peptide (TRP) are common. In contrast, only a single conserved TRP isoform, APSGFLGMRamide, has been documented in decapod crustaceans, leading to the hypothesis that it is the sole TRP present in this arthropod order. Previous studies of crustacean TRPs have focused on neuronal tissue, but the recent demonstration of TRPs in midgut epithelial cells in Cancer species led us to question whether other TRPs are present in the gut, as is the case in insects. Using direct tissue matrix assisted laser desorption/ionization Fourier transform mass spectrometry, in combination with sustained off-resonance irradiation collision-induced dissociation, we found that at least one additional TRP is present in Cancer irroratus, Cancer borealis, Cancer magister, and Cancer productus. The novel TRP isoform, TPSGFLGMRamide, was present not only in the midgut, but also in the stomatogastric nervous system (STNS). In addition, we identified an unprocessed TRP precursor APSGFLGMRG, which was detected in midgut tissues only. TRP immunohistochemistry, in combination with preadsorption studies, suggests that APSGFLGMRamide and TPSGFLGMRamide are co-localized in the stomatogastric ganglion (STG), which is contained within the STNS. Exogenous application of TPSGFLGMRamide to the STG elicited a pyloric motor pattern that was identical to that elicited by APSGFLGMRamide, whereas APSGFLGMRG did not alter the pyloric motor pattern. © 2007 The Authors.
Characterization of Yellow Family Proteins in Gryllus bimaculatus
Date: 2021-01-01
Creator: Alexandra W. Rubenstein
Access: Open access
- Neuronal plasticity occurs in developing nervous systems, with adult organisms rarely able to recover from neurological damage. The cricket, Gryllus bimaculatus, is useful to study neuronal plasticity due to its reorganization of the auditory system in response to injury beyond development. When a cricket ear is removed and auditory afferents severed, a rare phenomenon occurs: the dendrites of interneurons on the deafferented side cross the typically-respected midline of the prothoracic ganglion to form functional synapses with auditory afferents from the opposite side. To find proteins involved in this phenomenon, the Horch Lab assembled a de novo transcriptome from neurons in the prothoracic ganglion of G. bimaculatus. Differential gene expression analysis revealed upregulated protein yellows post-deafferentation, indicating these proteins could influence neuronal plasticity in the adult cricket CNS. I focused on characterizing the protein yellow family in the cricket. By relating protein yellows evolutionarily, mapping them onto the genome, and analyzing their sequences, I discovered the cricket has 10 yellow genes, including a newly identified yellow-r* and a block of yellows showing synteny with insect genomes. Additionally, yellow-e and -x in crickets are closely related to bacterial yellow, perhaps indicating a role for horizontal gene transfer in yellow gene evolution. The protein upregulated in the cricket CNS is closely related with yellow-f’s in other insects, indicating yellow-f is likely a secreted protein, highly expressed in the CNS, multifunctional, and conserved across insects. Characterizing yellow-f can give insight into how these upregulated proteins might be related to neuronal plasticity in G. bimaculatus.
Analysis of adhesion mutants in Arabidopsis thaliana This record is embargoed.
- Embargo End Date: 2025-05-14
Date: 2020-01-01
Creator: Bridgid Elizabeth Greed
Access: Embargoed
Genetic Population Structure and Accuracy of Morphological Assessment in Alosa aestivalis (Blueback Herring) and A. pseudoharengus (Alewife)
Date: 2017-12-01
Creator: Christopher Kan, John Lichter, Vladimir Douhovnikoff
Access: Open access
- Alosa aestivalis and A. pseudoharengus are herring congeners that are important forage species for piscivorous fish and birds. We measured population structure metrics for these species using microsatellite markers. The Southern Gulf of Maine study area allowed the assessment of these species at an inter- and intra-watershed level. We found no detectable population structure within or among watershed for either species which agrees with other recent research. Our results support regional-scale (e.g., Gulf of Maine) plans for management for A. aestivalis and A. pseudoharengus. We found that 5.4% of our samples were hybrids. Our study adds to a growing body of evidence that hybridization and introgression should be management concerns for these species, and precautions should be taken to preserve species barriers. An error rate of morphological identification was calculated by comparing morphological identifications against genetic classifications. We found an overall identification error rate of 16%, which differed significantly from zero (P = 0.008). Managers should also take note of the uncertainty in morphological identifications and adjust stock models and policies accordingly.
Salix exigua clonal growth and population dynamics in relation to disturbance regime variation
Date: 2005-01-01
Creator: Vladimir Douhovnikoff, Joe R. McBride, Richard S. Dodd
Access: Open access
- Willows are important riparian colonizers. However, the predominant models of early riparian colonization, which emphasize seedling recruitment, are inadequate to explain the success of these species in light of the extremely low rates of seedling survival observed. We used molecular fingerprinting markers (AFLPs) to identify and characterize Salix exigua clones on six sites, ranging in size from 850 to 1150 m2, located on two rivers. Clones as large as 325 m2 were detected, and an average of six clones per site occupied 75% of the vegetated area. Building on Mahoney and Rood's recruitment box model, we propose a model whereby prolific clonal growth allows for long-term colonization of riparian zones, and the balance between the relative importance of seedling regeneration and clonal growth varies based upon disturbance regime. A reduction in disturbance regime resulted in greater clonal growth and reduced genotypic variation. It is probable that, with an extended reduction in disturbance, the Salix exigua component would be represented by fewer, larger clones and would eventually decline significantly when these clones are replaced by taller and more shade tolerant species. © 2005 by the Ecological Society of America.